The paper you actually linked contains no such claim and contains absolutely zero occurrences of the word Inuit, albeit mentioning that the depigmentation of Greenlanders is much slower than might be expected due to alternative dietary sources. The web article at least does give fish as an alternative source of Vitamin D, but this only explains how a population would maintain its tone. Ergo, even in the absurd case of wanting to apply real-world biology to a fantasy setting, it's a moot point.

As for Dark Elves and snow... they live underground. This isn't an "they live in the north OR in caves", it's "they live in the north in caves".

Now, please drop the science discussion, I have to read papers often enough day to day without doing it when I'm looking at fantasy.