A model that is able to perfectly describe and (more importantly) predict everything is effectively indistinguishable from “reality”. Yes, there might or might not be a completely different, and maybe even weird, process underneath that gives rise to that model, but assuming that nothing whatsoever of that underlying process “leaks” into the model, it does not matter and may as well not exist for us.

Luckily, we’re still pretty far from a model which fully describes reality, and it may be entirely unobtainable for us. (Also, we only assume that spatial and temporal locality isn’t a thing, i.e. that the laws of physics are the same everywhere and everytime, so there’s that as well.)