[fortran77]

But there's some truth in this statement!

The "Luma" resolution is, in theory 625x625, but the "chroma" resolution is approximately 1/4 of that. That's OK, because the way our eyes work.

So "detail" remains at the 625x625 resolution, but the color information isn't that high. And our brains fill in the rest.

[tialaramex]

Digital video chroma sub-sampling literally has quarter chroma resolution in 4:2:0 video which is or at least was fairly common for live action stuff. It's obviously not going to be great for recording output from a computer, with sharp coloured edges, but live action scenes look fine.

I don't think anybody would claim that their 4:2:0 Blu ray has "low resolution" because it used chroma sub-sampling.