Indeed, it's almost impossible to turn your head slowly without your eyes fixing on points in your field of view, and then saccading to the next point. Try it. This is a hard-wired response. (You can perform some tricks to do it, like completely blurring your eyes, but that's not really the point.)
Meanwhile, if we watch a video with the camera turning, it's easy to keep our eyes staring straight ahead.
This shows that there is going to be a difference between a head naturally turning and watching a video of a head turning.
I think you're describing saccades as just being the "dropping out" of frames, and not including the extremely-relevant motion that our eyes do during a saccade.
I think the only thing I can say here is - I dont see anything weird when I turn my head, and when FPS games added blur to "character moves his own body", it felt much less natural, not more. So, to answer question a few posts up "how would we do it?" I'd just say "The way we always have before we got enough GPU to make everything look like a movie"
Actually I think motion blur is more of a (futile) attempt to hide low frame-rates because we don't have enough GPU to render the ever more demanding scenes.