It's the same with Free Will. Whether the universe has only deterministic laws, or a mix of deterministic and non-deterministic laws, Free Will doesn't follow: one way everything is predestined, while the other you don't truly have control of your actions, so neither way do you have full control of your actions. We already understand this now, and yet we carry on and pretend we have Free Will -- we have no real, appealing alternative.

It would be the same with proving that we live in a simulation, or that there is a god or gods, except as others have pointed out, we'd probably seek sandbox escapes.

Also, not every proof of being a simulation would necessarily be that. Any proof that our universe is a 4D projection of another with different dimensions might not include a proof of the direction of projection -- ours might be the true reality, and the other a projection of ours.