Thankfully, if there's any large company on Earth that really cares about perfecting UX, it's Apple.

I think part of the problem is the peripheral area where you wouldn't notice but still see is so thin that you don't save a lot. Maybe Apple has cracked it, though.

Might also be that peripheral vision is more sensitive to movement, and the edges where the lower res and higher res rendering meets could make for distracting discontinuities that look to the reptile brain (or the preprocessing in the retina/optic nerve/visual cortex) like a tiger...