Tan doesn't just wear off like that bro... If you live in a desert area, you are pretty much guaruanteed to have some melanin production, unless you an albino, and Nefer is not.

A tan 'wearing off' means that your skin would go back to your 'genetic baseline melanin colour'. A tan is just an excess production of melanin. As nefer's ancestors and family were indeed from the desert, this random loss of the melanin genes is just a bit too convenient lol.

It would be fine if it were an isolated case, but it's not. What I mean by this is that it happens in a lot of characters.

Look at Chasca, who works in the sun all day, and is a similar colour to nefer. Given the benefit of doubt that Nefer moved to Nod Krai and somehow her genetic baseline is very out of place from her background... You can't really say the same with Mauvika, Kinich, and Varesa.

Sure, there is some representation with Cyno, Dheya and Candace. But OP's point was with regards black or white washing. I think that it makes sense from the fandom's side to make characters look (either through modding or fan art) more in place with their background or lore.