It is possible the model calculates an approximate board state, which is different from the board state but equivalent for most games, but not all games. It would be interesting to train adversarial policy to check this. From KataGo attack we know this does happen for Go AIs: Go rules have a concept of liberty, but so called pseudoliberty is easier to calculate and equivalent for most cases (but not all cases). In fact, human programmers also used pseudoliberty to optimize their engines. Adversarial attack found Go AIs also use pseudoliberty.