>>281106018
>However it does end up being that the optical path is still not that short
Sorry, not optical path (which remains the same or similar as current headsets), I meant screen distance. 
Though the optical path might actually in fact be different. It would be the same if these were pancake lenses, but since one of the four prism components are magnifying a 1/4 size quadrant of the screen, the magnification power might be higher, which means focal length would be shorter.