If you look closely at those cutaway drawings of the Hangar Deck from TMoST you can see that the observation platform is not parallel to the flight deck. It angles downward whereas the horizontal lines of the shuttlecraft are parallel to the deck. So the drawing does look like a rendering for a forced perspective set. That would be significant if you intended to build an almost full scale set of the hangar deck, but building a miniature---even one about ten feet long---you don't have to build it with forced perspective. You just have to use the right lens when filming it.