They just went with the PHB/Sword Coast Guide or? You have options to make a High Elf, as Wood Elf and a Drow. And High Elves that look like either a Moon Elf or a Sun Elf (Wood and Wild Elf don't seem to be different in 5e anymore) in terms of skin, hair and eye colors.
The game generally seems lacking non-visual options and background information for your own character, and in comparison to what they have been doing for the companions. But visually I think you have all the options to make all the current major elf subraces in Forgotten Realms. Mechanically there is not difference between Moon and Sun Elves anyway.
Both Sun Elves and Moon Elves are technically classified as "High Elves" in some editions of D&D, but I prefer an actual separation between the two during character creation (e.g., showing "Sun Elf" or "Moon Elf" up-front on the character sheet) with an entry describing how they are both part of the "High Elves" despite their differences.
I agree, I just meant that in this case they are just following 5e. In the end it's part of the generally lack of customization for your own character. I really enjoy this game though, just that part is sadly lacking in my view. And on top of that, I find the visual representation of the elves not great. : )