and yet they are both dark and fair skinned, meaning they must have come from very different parts of the world (perhaps even antipodes). How does that make sense?
Yeah, that's a large part of why the (real life racial) diversity feels a little strange. It was the same in Witcher and I assume it's the same in the GOT prequel., haven't seen. They present it so nonchalantly like it's no big deal, a random variation that just happens and people barely even notice it. But that's not how human races work, they came around after a long, long time of near gentic isolation (and a little bit of ethnic cleasning as modern archeogenetics shows)
The fact that the "diversity" is so nonchalant and banal in those fictional universes implies that
a) there were once upon a time separate races, just like with actual humans, otherwise everyone would be just one, most likely black, race like the archaic humans.But it could be any race, you could pretend that in that universe, humans came around from arctic monkeys or whatever.
b) that the previously separate races have been at some point brought together, not so long ago that they would now be just one phenotype, but long ago enough that race wouldn't be an issue. BUT it that were the case, that would mean the we should see all kinds of mulattoes and mestizos and quadroons and all kinds of inbetweeners and hybrids. Just like in certain parts of Europe, cough Western Slavs cough, you can see all kinds intra-White hybrids. People have blue eyes, green eyes, grey, brown. Straight, wavy, curly, blonde, red, brown and even some proper black hair. All seemingly random (but of course, it's not, just pretty thoroughly mixed)
But as you say, it's a political statement, no amount of reasoning will accomplish anything here. I just find the "representation matters" schtick so annoying. Yeah kids can only relate to characters that looks EXACTLY look like them, even though time and again the most popular characters for kids are anthropomorphized animals. Also it makes no sense to say that racial representation matters and then act like well why are they mad at originally white characters recasts with non-whites? Race doesn't exist, checkmate Hitler. No, pick one.
Just occurred to me that the Elder Scrolls universe has a well executed example of racial diversity - the Redguards are effectively Africans, a human race from another continent that migrated to Tamriel. It is addressed, it is explained, it makes sense and it's fine.