[theptip]

I don’t think this suffices as disproving the hypothesis. It’s possible to play at 1400 and make some idiotic moves in some cases. You really need to simulate a wide variety of games to find out, and that is what the OP did more of. Though I do agree it’s suggestive that your first (educated) try at an edge case seems to have found an error.

This is broadly the “AI makes dumb mistakes” problem; while being super-human in some dimensions, they make mistakes that are incredibly obvious to a human. This comes up a lot with self-driving cars too.

Just because they make a mistake that would be “idiots only” for humans, doesn’t mean they are at that level, because they are not human.