I'm not saying Apple created a bad product...but I wouldn't expect a mere 23 million pixels to be indistinguishable from reality.
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.
It is probably similar with this as well, the question is where apple stands on this scale.