I have to disagree with your point a little bit.

Obviously you are correct, if the human eye can only resolve 4K, then a 4K and 8k image would be indistinguishable, the eye is the bottleneck. However, in my personal experience, this isn't quite true.

I can't play video games, whenever I try I get horrible headaches. I searched around and found out that the reason for this is the camera movement in a game. In the real world when I run, a lot of the images my eyes see are shakey or blurry... However my brain filters these useless images out.

When I play a video game however, this doesn't happen. Every jump, run, camera shake, motion blur, it is all pumped from the game, into my brain without being filtered. Ten minutes later I have a headache and need to rest.

That is a situation where the bottleneck for real events is different that the bottleneck when receiving images on a screen.

Or something like Cloverfield, the camera shake caused some people to become nauseous in the cinema. However those people could probably ride a bike on a bumpy road without a problem.

I have no idea why this happens and it seems completely counterintuitive, but the brain must be handling certain things differently.