They changed their name to Ren’dorei to reflect their new bond and embrace of the void, it’s a distinction from the other thalassian groups, just like how the blood elves changed their name to blood elves after the scourging. This does not change that they’re a sister group of the other thalassians or were part of one of the others before, they’re still thalassians and children of Quel’thalas, just a newly formed group with their own name. And even Alleria considers herself a Ren’dorei, she even says “we” when talking about the Ren’dorei.
This is also why I feel like the whole crowd going “there are high elves on the Horde” is a bit iffy, we have Thalassians on the Horde that is the majority and that control the kingdom of Quel’thalas. However, they changed their identity from high elf to blood elf and did have some cultural shifts and most notably allied with the faction that was not historically their ally.
The elves still identifying as high elves and not taking on the name blood elves still mainly remained with the Alliance, and are now a small group of exiles that don’t really like the blood elves. There’s a political rift here and their identity and story have diverged from the blood elves since the split. Even if they are both children of Quel’thalas.
Personally, I think this request was sated with the addition of void elves into the Alliance that has regular customization. Since I see no reason for adding another almost identical race to the game. Just like I don’t think forest/ice trolls should be their own race and instead be baked into troll customization.
Adding them as a race would also have the problem of needing to add something else since race parity is needed for the factions compared to customization.
The only downside in my mind of not having high elves is the possibility of the paladin class which I am very against since a strictly light-wielding class should not be playable on a void being. Just as if we had a strictly void-wielding class then it should not be useable for LFD (and maybe belves due to the holy sunwell connection). Priest gets a pass in my opinion since you can’t mechanically lock a whole spec from a race, that’s just not good gameplay, but it’s gameplay only, there are no holy void elves in lore and no shadow priest LFD.
However, if they added class customization that allowed for a void “paladin” then that’s a whole different thing.
But then again I don’t even think High elf paladin is a core aesthetic to high elves, we can literally count on one hand how many high elf paladins there are. The paladin order didn’t even have a lot of time to train non-humans before Quel’thalas fell too. Paladins only became a major thing for Thalassians when the blood elves formed the blood knights.
High elf paladin is a fan favorite but is not actually the core of the high elf aesthetic, rather the core “classes” of the high elves are Mage, Ranger, and Priest. Who are the classes we see the most of in wow lore. Paladin is more core to the blood elf aesthetic.
Now you can ask why High elf Paladin is so popular among the fans, but I think it’s because the people that mainly care about playable High elves are hardcore Alliance players, that’s really into the RTS games and/or lore. And Paladin is the Alliance class, so it makes sense that Alliance players and especially hardcore ones would want to play that class in a race they want.