> But what ever you do, you can only observe the behavior implemented by the game engine, and not the game engine itself, or the computer that is running it....

Yes, physics is about learning about the rules that the game engine implements. It’s not about learning about some reality outside our own, that’s the domain of metaphysics. Physics can’t answer questions about what is happening outside our own reality, and indeed neither can anything else inside reality because (as you pointed out) we can only test and observe what the game engine allows.