[FartyMcFarter]

That may well be true, but it isn't relevant. Game-playing engines are designed to win the position being played, not to maximize winning probability over its playing career.

Stockfish or AlphaZero don't care one bit about what happens in the next game they play.

[Vetch]

It isn't necessary either. In chess, as there's no need to worry about interactions between players' information sets, a player can safely apply pure strategies. Winnings approach being maximized over player career by trying to match as close as possible subgame perfect equilibrium from any given start node per game.