I admit that I find the "simulation argument" fascinating to think about but what I always wondered is what distinguishes a "simulation" from a universe whose physics is sort of structured in something like abstraction layers as ours seems to be? i.e. can you say Newtonian physics is a "simulation" built on top of quantum field theory and general relativity which are "simulations" built on top of the true theory of quantum gravity and so on
and if not, then what exactly does need to hold for a given universe for it to be characterized as a simulation, is it just about the simulation having some creator with intentionality and so on ... or is it about the degree of integrity/isolation/leakiness of the simulation layers?