For example, if chess is a win for white, you play black, and you have a halfway decent opponent, he will know what black's best defense looks like (that is: the one that takes him the most moves to win). Replaying that gives you zero chance of winning or drawing. Deviating from the beaten path cannot decrease that chance, and may increase it.
It is similar when chess, played optimally by both players, turns out to be a draw, and you want to win, but in that case, you may not want to give up your assurance of a draw, so you may play less weird moves. You still will want to play moves that lead to plays your opponent is weak at, though.
Sure, but the King's Gambit is just an opening, and you'd have to rely on lazy mistakes to guarantee a win 10 moves ahead that early in the game.
To the extent that an AI approaches perfect play more closely than a novice or masters from the 19th century, shouldn't we go learn from the AI?
One interpretation of Stockfish here is 'I don't think this is a very strong opening'. To the extent that it's correct, stronger players will not play that opening very much, so spending time to learn it seems potentially wasteful.
For perspective, Bobby Fischer created a version of chess which randomized the game because even in his day, he was annoyed that some players that he felt were far inferior at playing chess, could actually better memorize opening lines and enter the mid game with an advantage.
So the answer is that players very well have been learning from AI.
>To the extent that an AI approaches perfect play more closely than a novice or masters from the 19th century
AI has become better than even the top chess players of today.
And given that you want to become a better chess player, isn't it better to start learning the best lines from the start?