It's one of the single biggest misconceptions ever, it gets repeated endlessly
I don't think this is true, and engine evals aren't everything.
Two positions can have equal evaluations, but one can be trivial to play optimally and the other can be tricky and have a 10 move long sequence of "only moves" that are really hard to calculate. The latter is a much worse move, if you are not a chess engine.
still your move
If on move 29, you choose a move that is slightly worse but leave yourself in an extremely difficult position for you but an easy one for the other guy...
And then only on move 40 does the eval extremely diverge...
In my opinion, your real blunder was on move 29, not 40. Just because an engine could hold a position doesn't make it a reasonable move.
In practice, the move only added uncertainty for black. White faced easy choices, and black difficult ones.
I didn't disagree that Fisher thought the move was safe and miscalculated. Indeed, he didn't even miscalculate badly-- engines think they can hold the position.
I'm asserting that the move fails because it made the subsequent game more complicated for Fisher without imposing an equal penalty on his opponent. It made a bad miscalculation almost inevitable.
This is not something Black wants to do in matchplay chess in general. Usually he would be happy with a sterile draw and hope to take advantage of having an extra white in the remaining games.
Fischer, on the other hand, liked to play for a win in every game. And IIRC this match gave the defending champion draw odds, so the challenger had more incentive than normal to take risks, even in game 1.
Still, I generally agree with the analysis of Kasparov etc in this position. Fischer didn't miss the game continuation and he didn't assess the piece-down position as offering Black his share of winning chances. He more likely missed that after Bxh2 g3 h5 Ke2 h4 Kf3 h3 Kg4 Bg1 Kxh3 Bxf2 Bd2! White still traps the bishop.
In other words the correct calculation of subjective difficulty is a dot product, not simply a count of the number of equalizing moves.
It's hard to capture "obvious". One metric is how far you need to look down the eval tree to know a move is good, but even that is flawed.
This isn't true - that move takes the game from dead equal, to +0.7 (70 centipawns favor for Boris).
It isn't a total blunder but it's objectively a poor move.
Though this may be a situation where the weaker engine is actually more helpful in assessing the practical situation: +0.7 is a better reflection of the relative chances in a human game than 0.0.
I'm not qualified to analyse this, I read into it a bit more and apparently he was trying to complicate the game, the 1973 tournament book only marks it as ?!.
The engine knows what move would be a blunder for computer play.
It doesn't know what move made the position impossibly tricky for a human to maintain for black.
Every game that I analyze, there's possible moves where the computer will trade endless complexity for one's side for a couple centipawn advantage. These are moves that a human should not play.
I think the main point is that computers are so much better than humans at playing chess that what might be a reasonable move for them is effectively a terrible blunder for a human. It's like comparing a student driver with an F1 pro, and saying, "It's totally reasonable for the student driver to yank the wheel to the right when driving at 300 km/h, because an F1 driver would be able to recover from that." The point is that the student driver won't be able to follow up with near-superhuman ability to save the situation.
Of course, in this case, the engine doesn't think this is a particularly reasonable move; the evaluation just fails to show how bad it would be for a human-- even a near-superhuman chess player like prime Fischer-- to play.
FM Roese here (best DWZ 2399). I agree, figuring or even conjecturing that Fischer overlooked 30.g3 is totally insane. However he also did not saw the theoretical draw, this strikes me even more off. He never opened up about his idea, so in all likelihood he calculated something very stupid.
> if you plug it into an engine, it shows an equal evaluation
They criticized this argument rightly, but many basically repeated your mistake in the process of doing so. All engines use some evolved adaption of iterative refinement, be it either "Iterative deepening" (of an alpha beta search) [1] or "UCT" [2]. If you post computer evaluations you should at the very least give the reported nominal search depth and the engine name and version, otherwise you are just asking for trouble. On computer chess fora [0] they often post the whole log file bluntly.
[0] https://www.talkchess.com/