It’s an understandable position, but you are only half right.

On the iPhone’s screen, yes. Practically nobody could tell whether that is an 8K or 4K video.

But people who would actually like to capture 8K video already know that and what they intend to do is take that file out of the iPhone later on and watch it on an 8K TV or import it into a video editor on a computer. For those people, yes, 8K video capture would make sense.

Then it’s the obvious angle: if the sensor supports it, why doesn’t Apple offer it? The A16 is definitely powerful enough to process 8K/30 at the very least, most probably 8K/60 too.

Last but not least: it’s also about feature parity with the competition. A number of Android phones have offered 8K video capture for years. Not very effectively, granted, which is why this was an opportunity for Apple to show how it could be properly done. Chances are that it’s just saving it for the iPhone 15, which is a whole other discussion.