To simplify a bit, you get two options. Move A. Move B. From the best knowledge we have from our best engines, A is the better move (though I don't think we

To simplify a bit, you get two options. Move A. Move B. From the best knowledge we have from our best engines, A is the better move (though I don't think we have formally proven such yet). But if you play A, you are playing your opponent in a game of memorization. If you play B, your opponent loses any memorization advantage. Thus they must play based on ability other than memorizing responses. For a player whose memorization ability is equal or worse than their ability to play based on other ability, choosing move B is clearly the worse option. But if the player is one whose memorization is better than their other abilities at chess, then playing B means fighting them in an area they are worse at. The advantage of this can easily outweigh the disadvantage of move B compared to A in general. Imagine a military commander choosing an engagement over terrain more familiar to their side even though it is a worse engagement if both sides had equal knowledge of the terrain, because the terrain knowledge more than compensates for the negatives.