Exceedingly elaborate, internally-consistent mind constructs, untested against the real world, sounds like a good definition of schizophrenia. May or may not correlate with high intelligence.

We only call it "schizophrenia" when those constructs are utterly useless.

They don't have to be. When they aren't, sometimes we call it "mathematics".

You only have to "test against the real world" if you don't already know the outcome in advance. And you often don't. But you could have. You could have, with the right knowledge and methods, tested the entire thing internally and learned the real world outcome in advance, to an acceptable degree of precision.

We have the knowledge to build CFD models already. The same knowledge could be used to construct a CFD model in your own mind, if only, you know, your mind was capable of supporting such a thing. And it isn't! Skill issue?