What bothers me most is that they equate a model with reality.

Quantum gravity theory is our current working model that we use to describe our observations. It’s not reality itself, and no scientist worth their money would claim that it is, because if it was, physics would be solved and it isn’t.

That’s how science works: We have observations, we build models to describe them, then we have more observations that don’t fit the old models, so we build newer models that also describe the new observations. Since we aren’t omnicient, there’s always something we can’t observe (yet) and what we can’t observe we also can’t describe.

“Therefore, no physically complete and consistent theory of everything can be derived from computation alone.”

This, in fact, would fit quite well to an imperfect simulation that doesn’t perfectly follow all the rules we made up when observing.