Character Creation Has A Race Problem

[Nandina]

In Eorzea and with the other races...that point is moot. We don't know the intensity of ultraviolet radiation, or even whether it's needed. They may be producing vitamid D through the use of a different chemical reaction, they may get more of it from food or they may just not even need it to begin with.

Appeal to ignorance fallacy. You can't use what you don't know to justify why something can or can't happen, because it literally proves nothing. Using your logic, I could say that the ultraviolet radiation could be the same as ours in real life to justify why we should get more differences, but that's a weak argument.