I have a little trouble understanding what you're trying to say here but I don't think it's really accurate. Positionally tracked headsets like the Vive and Rif

I have a little trouble understanding what you're trying to say here but I don't think it's really accurate. Positionally tracked headsets like the Vive and Rift do not model vision as if our eyes are permanently stuck forward. They are very much intended to be used with normal eye movement within the field of view of the headset while the head is stationary. Both are low persistence displays with a 90Hz refresh rate. Low persistence was an innovation from Valve explicitly designed to reduce blur and ghosting resulting from eye motion relative to the display as you get when fixated on a stationary virtual object while turning or moving your head or when trying to track a moving virtual object with your eyes while keeping your head still. In an ideal world we would have even lower latency head tracking and higher refresh rates but current headsets already allow for legible text when moving your head thanks to low persistence. I'm not familiar with the Minecraft hack you mention but approaches to snapping view changes are generally designed to address issues with using a controller rather than actual 1:1 head motion to change view orientation. View rotation independent of head movement tends to produce nausea due to the disconnect between visual cues and cues from the inner ear but really has nothing to do with any supposed assumption of eyes being stuck forward relative to head orientation. Issues with convergence, accommodation and depth of field raised in other replies do still exist with current display technologies but they are again not particularly tied to any assumptions of fixed eye orientation.