One problem is that gravity is universally coupling, so no part of the universe is technically "unobserved." I suspect that we could look back at the dynamics of large scale systems and see deviations from GR if the simulation were neglecting any part of the universe in the absence of observation/interaction.
If I were building a simulation I would just have not made gravity universally coupling because it makes it hard to chunk reality up into parts. Thus it seems like the universal coupling of gravity is evidence against a simulation hypothesis.
If I were building a simulation I would just have not made gravity universally coupling because it makes it hard to chunk reality up into parts. Thus it seems like the universal coupling of gravity is evidence against a simulation hypothesis.