Bill,

In English it implies the crucial point of a shape - a static thing. In that sense we would find nothing wrong with Black 27 I'd suggest. It is the crucial point of the shape.

But in Japanese the term kyuusho is the "urgent point". It's a dynamic, time-based comment.

For "timing" I know less heuristics.

Bill,

First, a minor point. GoGoD has 11 games with this position and in 2 of them the second-line 24 is played. Both examples were in China, just after the Rin-Takemiya game, which hints at them thinking this was an important on the Japanese play. Takemiya appeared in 4 of the 11 games, so it was clearly a stylistic choice as much as a joseki choice in his case.

But the major point may have to do with 27. The Japanese commentary on this game does not mention 24 but does mention 27 and says it is the "vital point". In another Takemiya game of the same period, the commentary does not mention 24 or 27 but does mention that White was remiss in not grabbing the vital point at O13.

It seems to me that "vital point" is another term that will have to be arraigned before the hanging judge in the light of AI evidence, but for different reasons in Japan and the English-speaking world.

In English it implies the crucial point of a shape - a static thing. In that sense we would find nothing wrong with Black 27 I'd suggest. It is the crucial point of the shape.

But in Japanese the term kyuusho is the "urgent point". It's a dynamic, time-based comment. And one thing I've noticed about very many AI plays that surprise humans is that they are based on a different time frame from our usual one. I think this game is a case in point. Often bots play moves earlier than we expected. Often later. They often play (or accept) the pro move but at a different time.

"What if the bird won't sing?"

Katago (newest 40 block) seemed to agree with Elf when I set up the situation for White 24. However, there was a slight question remaining. Katago had blue as S15 but it assigned nearly as high a value to M15, the point where Takemiya finally played 27. So let's just wait a while... (remember my box kind of lumbers along under the weight of the 40 block). Well surprisingly, suddenly (around 40K playouts in this case) M15 turns blue! Katago does not agree with Elf, except that Rin played the wrong move for 24.

, is there a Japanese term for this sort of move,

I'm not 100% certain I know what you are referring to - one swallow doesn't make a summer and all that - but with that caveat it looks like you're talking about kaname ishi - linchpin stones. They are contrasted with kasui shi - dregs stone.

The contrast most often comes backed up by a pair of provers: Kaname ishi wa suterubekarazu - Don't give up linchpin stones, and Kasu ishi nigerubekarazu - Don't run away with dregs stones.

Kaname ishi are reasonably common in go commentaries, but tend not be classed as a technical word (i.e. requiring a definition) simply because the term is part of ordinary Japanese (meaning a keystone or corner stone). Kaname itself means pivot, and so you could say "pivot stones" but that runs the risk of treating only cutting stones as kaname ishi. That is certainly a common application, but usage can be much broader. It refers to stones that may look heavy and therefore disposable but which are not in fact disposable. The reasons for not treating them as disposable can be rather subtle and on a grand scale. I've noticed AI bots make lots of kaname ishi, and I've noticed that simply because many of these moves have surprised me.

In one way I really shouldn't be surprised. One of the most sublime examples is the very famous three-stone shoulder hit by Go Seigen in Game 1 of the Kamakura match. There, the stones were not disposable because they were causing too much of a nuisance to Kitani, who felt obliged to capture them - but couldn't, as Go had observed, it takes too many moves to do that. Go, of course, had also realised that they stones were not as heavy as they might have looked, because leading them to safety did not cause collateral damage (these three stones were also a sublime example of the proverb 'five alive').

I remember looking at that game several times, and each time not understanding the significance of those three stones. For me, they seemed like kikashi: Black answered below, so there is no loss in throwing them away. Definitely not key stones. I always thought that maybe there is a lesson here that I failed to understand.

Now with bot analysis, one might be tempted to say that I was right, but I do not think that it is so easy. There must be some merit to the moves Kitani made, it's just that other aspects dominate at that point in the game. One thing to notice is maybe that White turning where Black “crawled” would have quite an impact on the development on the right side. Maybe it is interesting to take a look at what happens in that area, and when, if the bots have their way.

As to the function of kaname ishi, a word association I like to use is "disruptive". I see a lot of AI play as disruptive, whereas as humans have an urge to be creative (literally so, rather than imaginative). And that should come as no surprise. Go is game of alternating turns. At literally very single step of the game, the opponent is disrupting what you have just tried to create. Learning to handle that disruption is very hard - as Kitani found. I have no idea how to do it, but I sense it may be a matter of mindset rather than technique.