[verall]

It's not just that the eye is less sensitive to chroma.

Although your 4:2:0 subsampled 1080p video only has 540x960 pixels with chroma information, the decoder should be doing chroma upsampling, and unless its a super simple algorithm it should be doing basic edge detecting and fixing the blurry edges chroma subsampling is known to cause. I posit that even with training, without getting very very close to your screen you wouldn't be able to tell if the source material was subsampled 4:2:0, 4:2:2, or 4:4:4.

The truth is that generally people DO subjectively prefer high resolution source material that has been downscaled. Downscaling can clean up aliasing and soften over-sharp edges.

People who watch anime sometimes upscale video beyond their screen size with a neuron-based algorithm, and then downscale to their screen size, in order to achieve subjectively better image quality. This is even considering that almost all 1080p anime is produced in 720p and then upscaled in post-processing!