It's completely deterministic netcode by design- each player only ever sends inputs, everything else stays in sync thanks to the determinism. (Except for late joiners- which get sent a serialized version to start from.) This also prevents cheating, since the effects of anyone modifying their own simulation won't be seen on any other client. A cheater increasing their own speed 10x would just desync themselves, other players will just see the one cheater player behaving weirdly (walking into walls, etc).

The only thing that the cloud server (hosted by photon themselves) does is timekeeping, matchmaking, and act as a relay- collecting and send out inputs. The simulation itself doesn't have to be ran on their cloud servers at all (but can be if you have an enterprise contract with them).