It will definitely not be indistinguishable from reality, but might be good enough to fool us after a short getting used to, similarly to how even 24fps is enough for continuous motion. Of course you will see 60fps as more “fluid”, but only in comparison. And afterwards the differences quickly plateau and not many people can see any difference between 120 and higher.

It is probably similar with this as well, the question is where apple stands on this scale.

The human eye actually has terrible resolution. We only see in high resolution in the fovea in the very center of our eye -- basically the single point of primary focus. Resolution beyond that drops off dramatically (1/7th and much worse).

I've seen people claiming on sites like Reddit that people who watch with CC on simply read it in their peripheral vision while focused on the action, and that just isn't possible in most situations for the reason I mentioned. You actually only see high resolution in the middle 1 degree of angular view.

So to come up with such a number someone took the entire FOV of the human eye and assumed that you focus your fovea on each and every angular degree of it.

That's neither here nor there are your point is as valid -- where you're focused on will have a pixel density below "reality" for your fovea, however it presents lots of optimization potentials in software (e.g. no need for fine rendering outside of the focus) and in hardware. There are already devices which use tiny mirrors and optics to basically concentrate the pixels wherever you're looking and render a distorted view to match.