Pretty normal. I mean, black is not allowed to resign, and passing when you're behind is the worse possible move, so it makes sense black try stupid things.

This is a training game from LeelaZero from yesterday.
It lasted for 623 moves!
What I found even more interesting was LeelaZero's "under the stones" strategy with black - see move 365 for instance, where instead of capturing two stones with P9 (which is not enough to win for black), it fills in a point, lets white capture that huge group, then later starts playing in the empty area created by the capture in an attempt to narrow the gap

Black does that several times in fact, with multiple groups, ending up with all the stones dead.

Somebody should tell LeelaZero that this strategy doesn't work

And I expect that LeelaZero will soon learn that Black's strategy does not actually increase already remote chances of winning.

No chance.

I mean, if Black pass, its winrate is exactly 0%. If black has 0.000001% chance to win by playing, then it's logical to play. LZ has no reason to learn to pass like we humans do.

Here in this training game (less than 7 days ago) {sgf omitted} LZ only passed because it didn't have a legal move available

but why doesn't white pass earlier?

Has LeelaZero always played like this, or is it just that sorin did not notice until now?

My impression is that Leela Zero was more reasonable about passing until it started learning from the games of ELF, who passes a lot less (my understanding is that the ELF code handled passing specially, while Leela Zero learned it naturally in its neural network).