I don't see why that is a problem.. they are the same lorewise. Peopel just like to complain while some expect blizzard to do einredible detail on everything. Many just wanted to play high elves or have a decent model on the alliance for a change.
Many of these sub-race groups are not created to be some brand new race, just minor variations at best. Some of the people calling for races like Nightborne, Highmountain to be even more distinctive don't get why they exist. Nightborne for example are a Highborne led Night elven community on the pre-sundering culture that hasn't been shown yet in game, but has in-game groups like the shen'dralar of that disposition - they were just never shown it in game, we are just told (Dire maul isn't updated or repaired, and blizzard don' build a new city for the fabled group. But blizzard ended up doing it when they did Suramar, and decided they would make the night elves in it a new modified type..that's it.
It's not a new race, it's not something completley different from what the lore we know of Night elven cultures is. (Yes NElves have more than one type of culture - in fact most realistic races would) and they would have various nations, even minor superficial differences like irl has peopel with skin colour and facial feature variations.
Blizzard don't have to distinguish high elves from blood elves any more than they have in terms of models. They are meant to be the same race, void elves just a variant , the main differences are in the story, they can be political, or ideological, or historical etc, there are differences but they don't have to go out of their way. I think they've acheived what they want with them and most players anyway wanted to have these other groups as they saw them when they were introduced in game as NPC races. That's why sub-races were extremely popular.
Without doubt some people are going to be disapointed wanting a full race from what is essentially a sub-faction or sub-race, but hey blizzard accomplished what they wanted. I am one of the players that would like more details and differences, but I'm okay if I don't get it for the purpose of these races, I wouldn't be disatissified or rage at blizzard for doing a crap job or anything like that.
Besides, I think they did well with void elves having a different look that gave them a vibe that fit the theme. Now the interesting stories can start, and it would serve them well if they do good ones.
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Yes, high/void elf lore would be good, lots of things they can do there, with the two being different but also similar. I still would like to see void elf night elf interactions and friendships develop, and we could have void elves lean towards the night elves now while high elves take their place as the human friends they've always been.
I'd like more explroation of the dark side of the moon and Elune's void side and this should draw void elves to the night elves, whether faith based or intellectual driven or both. Would be nice to see more.