johny lee system keeps game fov and fov that the screen takes from your eyes equal to achieve a vr effect
6dof doesnt do that
edit:
current 6dof simulates looking at an screen
lees seem to be looking through a window
in fact the tech is what ww2 gunsights used
edit:
6dof to work properly :
if an image takes 10 pixels when youre at 1 m distance from the screen, it should take 5 pixels when you are at half meter
this is old tech gunsights work this way however distance to the glass always same apparent size of the crosshair
6dof doesnt do that and honestly seems quite lame to me not having implemented this yet