This is true (well, the optics erect an image of the displays at a fixed focal distance of a couple meters), so you certainly don’t need more than one prescription.
But this is one of my bugbears about the idea that stereo displays are “3D”. In real life, you experience space through focusing and depth of field, which responds to your pupils and lenses; that doesn’t happen with current headsets at all. I doubt it’s good for your eyes, and it certainly makes close-up objects look wrong.
(Which is another reason they’re right to make this thing all about UI in the 1–5m range, and not pretend it can just simulate any old environment)
