Basically, I fail to see why anyone would create such a detailed simulation if it bore absolutely no resemblance to reality.

I have seen simulators of Conway’s Game of Life (or similar) that contain very complex things, including an actual Turing machine.

I could see someone creating a simulator for CGL that simulates a Turing machine that simulates a universe like ours, at least as a proof of concept. With ridiculous amounts of computation available I’m quite sure they’d run the inner universe for a few billion of years.

If by accident a civilization arises in the bottom universe and they found some way of “looking above” they’d find a CGL universe before finding the one similar to theirs.