I saw that vid and thought of a few problems. For one, doppler. Also, he's saying that if c is different in two directions, then so too is time dilation. If that's true, then so too is length contraction, which means it's meaningless to even say the light travelled the same distance in both directions. In fact, if time dilation is balancing it so it appears c is the same, even if it is not, then length contraction must balance it, which in turn means c was constant after all.

Basically it's clickbait. I like veritasium a lot, I watch his uploads as soon as they are released, but it's his job to find things to talk about. I think he's getting a bit thin on ideas, frankly.

And yeah, the CMB is a problem too.