It's almost like a miracle! You can get 4:4:4 video from 4:2:0 video - if you downsample from 4K. Michael Ma shows how it's done in this video
It's true - you really can perform this miracle and it does improve the quality of your HD video.
Michael Ma, from the Daily Note, was probably motivated to make this video because his site is devoted to the Galaxy Note series of "phablets". Horrible word, great concept: a phone that's actually big enough to use, has a massive battery, and, it its latest incarnation, the ability to take 4K video.
Anyway, it's a really good explanation of what's going on, and it applies to all types of 4K video making - whether you're using a phone or a camera that costs thousands of pounds.