Yeah, but that's the only family they making an actual plot point about. The Targs be like "Fuck those bastards," and it's done. For the Velaryons we get the Westeros version of that sitdown between TO and his dad.
That's why I said it wasn't intentional. Thougth, if I'm not mistaken, House Velaryon is related to the Summer Islands. That's why they are tied to ships so much. They probably shouldn't look like they do in the show, but saying they are white might be a stretch too. I think Martin himself said that it's reasonable to think of them as being black.