It may be true that only 4:2:0 is actually being used, but I'd have thought 4:2:2 would be included on the receivers, it would be silly not to!
Don't think it matters too much, as you wouldn't "really" notice the difference, resolution being mainly in the luminance Y component. That said, I'm not personally in a position to do a visual comparison!
(After MPEG4 compression. any supposed difference may actually be irrelevant!).