Not necessarily, it's enough to have some notion of finiteness of computational resources for the outside, in whatever form they may appear. This is a pretty small assumption as we don't know any system which doesn't behave this way. So, by Occam's Razor, why postulating new physics (simulators without any kind of resource finiteness) if we can explain what we experience with traditional physics?

Also, if in the future we start simulating universes, all these constraints will apply to us and all the simulations we do.