I mean, the creator of a simulated universe isn't omnipotent though, for two reasons: first, there are plenty of things that they cannot do in their own universe, being just some regular person there, but more importantly, there must be limits on what they can do in the simulation, because that simulation has to exist on a computer which presumably has finite hardware limitations. "Framerate" or equivalent won't matter as much because time doesn't have to pass at the same rate, but the computer still is only going to have so much storage and memory space, or whatever equivalent the technology involved uses, and so nothing that would exceed those limitations can be done in the sim.