[harpastum]

I think your math is correct, and it will be very limited compared to a real-life retina screen, but I think there's also a perceived resolution increase from having binocular vision and moving.

If you hold your head steady while looking through a window with a plastic screen on it, things outside are obstructed. If you move your head slightly back and forth and focus in the distance, the screen pretty much disappears.

Your brain can do some motion smoothing to determine the "actual" content, even if it's sampled. I'm not sure how you could quantify it, and it only helps a relatively small amount, but it's there.