The problem is that those experiments would invalidate only their assumption about the supposed structure of the supposed simulation, not the overall idea of the simulation. So the statement overall actually is non-falsifiable.

This is like saying "there are invisible elephants walking everywhere, let's try to see if they are made of neutrinos".

>So the statement overall actually is non-falsifiable.

Except if all possible structures of all possible simulations must by necessity fit those assumptions.

Which is their fuller argument.

It seems like a silly argument. The physics of the outer universe are not bound by the rules of the inner universe. From the perspective of the inner universe, we can never hope to deduce facts about the outer universe based on out observations.

And yet we already impose other rules onto our own universe not deducible by the universe itself, like e.g. logical consistency.

Why not expand them to any possible external universe?