No-castling chess didn't need to be trained from scratch. Starting with a trained or partly-trained AlphaZero would certainly have worked, since no-castling che

No-castling chess didn't need to be trained from scratch. Starting with a trained or partly-trained AlphaZero would certainly have worked, since no-castling chess is a strict subset of chess. The only reason not to is if you are DeepMind and training resources are really cheap. For more esoteric variants like this, it makes sense to start from scratch, though eventually you could imagine an AI that is good at adapting to all perfect-information two-player games, or even others.