Flight physics don't scale down (or up) well. It's the predominant reason small airplane and quad models have enormously unscalable performance characteristics and abilities.

Making it bigger doesn't "just work"... same for the inverse.

X-Plane really only SORT of models flight. There is no actual FEA or fluid simulation of any kind. The airfoils are canned data lookup. So you can't make something out of polygons and have it wactually "work". It'll fuselage calculate drag based on frontal area and the coefficient you specify, but that's about it.

This approach works well for real planes since 99.999% of them use standard NACA airfoils that are well documented in the public domain.

Many people have attempted, but its still and unsolved problem with fluid physics.

Maybe we're already living in it? ;)