The human eye can see higher than 4K in the fovea centralis — or area of highest resolution — which subtends a circular region about 2° across in the center of the visual field.
If the target is stationary against a stationary background, you don't have much choice but to move that 2° high-resolution region across the area of interest step by step, making sure you give each spot a good, thorough examination, because if you miss what you're looking for when you happen to be looking right at it, you won't be coming back to it again.
In humans, the visual field is about 160° x 100° (width x height) without turning one's head. Even if we say (as in this case) that the vertical field is less than the whole 100°, that still means we have to check something on the order of a thousand fovea-sized angular regions, spending second or two on each one.
One thousand seconds is more than a quarter of an hour.
Yes yes. Lovely science. All of which is impossible to do with a video at that resolution. So his point stands.