Yeah, when we use the term “Motion Projection” what we are actually referring to is extrapolation. Where the new frame generation feature on the 4090 is interpolation.
With extrapolation, the algorithm is inferring on previous frame information and drawing a new frame (in to the future). This comes with an unavoidable risk which is some of the pixel data could be wrong when the next real frame is generated. This is especially true on edges of geometry… which is why you see “wobbles” or shimmering on the edges of the render window, or where the aircraft air frame meets the window, or on the trailing edge of the wing, etc. But the benefit of doing it this way, is lower latency, which is desperately required in VR.
With the 4090 frame generation, my understanding is that it is interpolating. Which is inferring information from two real rendered frames and inserting a fake one between them. This comes with a huge downside obviously, as the GPU needs to process 2 frames first in the frame buffer, insert the frake frame between them and THEN draw to the display. This takes more time, thus latency, and could induce motion sickness, particularly if this is tied to head motion. The benefit here is that you get a lot more consistency, less artifacts or “wobble” because you have two real frames to work with.
Do with that what you will, but it sounds like there is a real technical hurdle here as it pertains to latency.