There's a variety of different attestation strategies folks have cooked up! For example this crate has some tools, https://tangled.org/ngerakines.me/atproto-crates/tree/main/c...

So far they are mostly trusted authority rather than peer systems. But, since each player owns their own PDS state, one could perhaps just hash the previous state they are working off of. That can at least detect if a game is consistent/agreed to by both sides, allow one player to detect the other's tampering.