I'm curious what version of KataGo you were using, and how many playouts / what komi you tried. Similarly LZ.
Did the bots actually miss jlt's sequence, or did you interpret them evaluating most of jlt's sequence as good for white (except for the very last bit) as missing jlt's sequence? Because in fact most of that line *is* good for white. It's possible that they hadn't missed it at all, but evaluated it as good for white because they went on to read the ko as the counter to jlt's sequence and evaluated the ko as winning!

- Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . X X O X . . O . . . . O O . |
$$ | X X X X . X O X X . O . O O O O X X b |
$$ | X O O O X X O O O , . O X X X X . . c |
$$ | X X O O O O X . O X . O X . . . a O . |
$$ | O O X O . . X . O O X X X . O . X X . |
$$ | . . . . . . . . . . O O O X O O O X . |
$$ | . O O O . . . O . . . X O O O X X . . |
$$ | . X O X O . . O . . . X X O X O X . . |
$$ | . O . X O . O X X , O X O X X , X . . |
$$ | . X X X . O X . . . . X . . . . X O . |
$$ | X . . X O O X . . . . . . X . . X O . |
$$ | . X X O O X O X X O O O O O X X O . . |
$$ | X X O X X X . . . X . X . . X O O . . |
$$ | . O O O X . . . . X . X O O X X O . . |
$$ | . . O , X . . . . , O O X O O O . . . |
$$ | . O . O X . . . . X X O X X . X O O . |
$$ | . . . O O X X X . . . X . . . X X O . |
$$ | . . . . O O O X . . . . . . . . . . . |
$$ ---------------------------------------[/go]
I think the summary of the situation is that "b" and "c" are about the same and both work simply and easily. "a" is one point better, but is very complicated because if black resists, it requires a messy ko fight.
I'm playing around with the latest public 40 block KataGo net, mid thousands to low tens of thousands of playouts clearing the cache a few times to see what it thinks on fresh retries ("clear_cache" in GTP console) on Japanese rules ("kata-set-rules japanese" in GTP console, Lizzie will not do this automatically for you) and I get the following results:
- Japanese rules, 7.5 komi or higher: White is clearly winning (by bot standards) and can just play "b" or "c", which is good enough to win: 85%ish. Trading 1 point for simplicity. Clearing the cache and repeating seems to result in it picking b with decent reliability for me, although not 100% consistent.
- Japanese rules, 6.5 komi: White is favored (by bot standards) with "b" or "c", but it's less clearly winning. 65%ish. Clearing the cache and repeating seems to result in it picking "b" or "c" most of the time. Here KataGo has a little bit of "blindspotness" by failing to play "a". Based on the variations it gives, I think sees jlt's line easily, and furthermore sees that white can counter with a ko, but initially doesn't see quite right way to start the ko and/or feels it's messy enough that it would rather go with the 65%ish moves. If you actually play "a" on the board then the winrate quickly goes up to 75% to 80%, since now it's found the right way to start the ko and is reading it deeply enough to see that white can fight it well, in which case missing "a" is clearly a mistake. But if "b" or "c" still win by 0.5, then at least maybe it's not a mistake that costs the game yet.
- Japanese rules, 5.5 komi: Now white is actually losing if playing b or c, probably by half a point. So KataGo seems to consistently choose "a" now. Again, it's already seen past jlt's issue to seeing that white can counter with ko, and however messy the ko initially appears, it's better than playing "b" or "c" and heading into a losing endgame. And with several thousands of playouts, it thinks the ko is eventually winning for white by a bunch, so black must not descend and instead must fight the normal endgame, where maybe white has a bare lead, by 0.5. (60%).
The ko line looks like this. White goes for the extra point, and black resists like jlt showed.

First
- Click Here To Show Diagram Code
[go]$$Wc First
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . X X O X . . O . . . . O O 6 |
$$ | X X X X . X O X X . O . O O O O X X 4 |
$$ | X O O O X X O O O , . O X X X X 5 . 3 |
$$ | X X O O O O X . O X . O X . . 2 1 O . |
$$ | O O X O . . X . O O X X X . O . X X . |
$$ | . . . . . . . . . . O O O X O O O X . |
$$ | . O O O . . . O . . . X O O O X X . . |
$$ | . X O X O . . O . . . X X O X O X . . |
$$ | . O . X O . O X X , O X O X X , X . . |
$$ | . X X X . O X . . . . X . . . . X O . |
$$ | X . . X O O X . . . . . . X . . X O . |
$$ | . X X O O X O X X O O O O O X X O . . |
$$ | X X O X X X . . . X . X . . X O O . . |
$$ | . O O O X . . . . X . X O O X X O . . |
$$ | . . O , X . . . . , O O X O O O . . . |
$$ | . O . O X . . . . X X O X X . X O O . |
$$ | . . . O O X X X . . . X . . . X X O . |
$$ | . . . . O O O X . . . . . . . . . . . |
$$ ---------------------------------------[/go]
Next white cuts!

Next
- Click Here To Show Diagram Code
[go]$$Wc Next
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . X X O X . . O . . . b O O X |
$$ | X X X X . X O X X . O . O O O O X X X |
$$ | X O O O X X O O O , . O X X X X O . O |
$$ | X X O O O O X . O X c O X . . X O O e |
$$ | O O X O . . X . O O X X X . O 1 X X . |
$$ | . . . . . . . . . . O O O X O O O X d |
$$ | . O O O . . . O . . . X O O O X X a . |
$$ | . X O X O . . O . . . X X O X O X . . |
$$ | . O . X O . O X X , O X O X X , X . . |
$$ | . X X X . O X . . . . X . . . . X O . |
$$ | X . . X O O X . . . . . . X . . X O . |
$$ | . X X O O X O X X O O O O O X X O . . |
$$ | X X O X X X . . . X . X . . X O O . . |
$$ | . O O O X . . . . X . X O O X X O . . |
$$ | . . O , X . . . . , O O X O O O . . . |
$$ | . O . O X . . . . X X O X X . X O O . |
$$ | . . . O O X X X . . . X . . . X X O . |
$$ | . . . . O O O X . . . . . . . . . . . |
$$ ---------------------------------------[/go]
White has time to cut here because it gains white a liberty via the cut at "a". If black tries "b" for example, white will play "c" and kill the big black center group, winning 4 liberties to 3. Black can play "d" or "e" to make it a ko instead... but even though this isn't the ko white is "expecting", it's just as winning for white as the other expected one.

Next next
- Click Here To Show Diagram Code
[go]$$Wc Next next
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . 5 4 3 |
$$ | . . . . . X X O X . . O . . . a O O X |
$$ | X X X X . X O X X . O . O O O O X X X |
$$ | X O O O X X O O O , . O X X X X O . O |
$$ | X X O O O O X . O X c O X . . X O O . |
$$ | O O X O . . X . O O X X X . O 1 X X . |
$$ | . . . . . . . . . . O O O X O O O X . |
$$ | . O O O . . . O . . . X O O O X X . . |
$$ | . X O X O . . O . . . X X O X O X 2 . |
$$ | . O . X O . O X X , O X O X X , X . . |
$$ | . X X X . O X . . . . X . . . . X O . |
$$ | X . . X O O X . . . . . . X . . X O . |
$$ | . X X O O X O X X O O O O O X X O . . |
$$ | X X O X X X . . . X . X . . X O O . . |
$$ | . O O O X . . . . X . X O O X X O . . |
$$ | . . O , X . . . . , O O X O O O . . . |
$$ | . O . O X . . . . X X O X X . X O O . |
$$ | . . . O O X X X . . . X . . . X X O . |
$$ | . . . . O O O X . . . . . . . . . . . |
$$ ---------------------------------------[/go]
So in response to the cut, black must protect right away. The result of being able to interpose this cut of course, is that now the ko is extremely heavy for black because the center group is at stake.
Then white initiates 3-4-5. At this point, if black immediately begins fighting the ko with "a", it's immediately losing, so KataGo starts suggesting moves all around the board to try to generate bigger threats, but KataGo isn't optimistic about it. (80% for white).
So instead we get this:

Black can't fight ko so must back down
- Click Here To Show Diagram Code
[go]$$Wc Black can't fight ko so must back down
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . X X O X . . O . . . . O O . |
$$ | X X X X . X O X X . O . O O O O X X . |
$$ | X O O O X X O O O , . O X X X X 5 . 3 |
$$ | X X O O O O X . O X . O X . . 2 1 O . |
$$ | O O X O . . X . O O X X X . O 4 X X . |
$$ | . . . . . . . . . . O O O X O O O X . |
$$ | . O O O . . . O . . . X O O O X X . . |
$$ | . X O X O . . O . . . X X O X O X . . |
$$ | . O . X O . O X X , O X O X X , X . . |
$$ | . X X X . O X . . . . X . . . . X O . |
$$ | X . . X O O X . . . . . . X . . X O . |
$$ | . X X O O X O X X O O O O O X X O . . |
$$ | X X O X X X . . . X . X . . X O O . . |
$$ | . O O O X . . . . X . X O O X X O . . |
$$ | . . O , X . . . . , O O X O O O . . . |
$$ | . O . O X . . . . X X O X X . X O O . |
$$ | . . . O O X X X . . . X . . . X X O . |
$$ | . . . . O O O X . . . . . . . . . . . |
$$ ---------------------------------------[/go]
And this leads into a very, very close endgame (at Japanese 5.5 komi) where white has the barest advantage and is hoping to win by 0.5.