Veressa Windrunner gets attention when her story supports her wider family for the most part.
Elven Unification, and the meaning of it, are still up for debate but the expansion is focused on the Blood Elves and the Void Elves, whose light and void alignment mirror the story of the expansion. Expecting Elven unification to mean more than Void Elves and Blood Elves is to give Alliance High Elves an importance they have not earned.
Alliance High Elves are present in Silverglade Refuge, to which the Horde has access. Windrunner Spire is still within the Kingdom of Quel’thalas. These groups don’t ‘CONTROL’ these areas in spite of the Horde, they are permitted to be there and they implicitly accept they are living under Horde sovereignty. If they ever betray that, it wouldn’t take much effort to clear them out. Control is the ability to hold onto something. If you are instead allowed to do something by others, then THEY have the control.
The expansion cosmetics are based on Blood Elves (who are High Elves) and Void Elves. In other words, there are two, not three, aesthetics. There being a blue colour scheme on the Blood Elf gear does not make that Alliance High Elven.
The Amani Trolls are unlikely to be made an allied race because they are not at the same level of complexity as the Haranir and Earthen, who are the gold standard of allied race customisation right now and who highlight that other races need to be brought up to that standard. Nor is it guaranteed the Amani would join the Horde should that unlikely choice be made, it is far more probable the Amani would be neutral, just as Earthen were. Either way, you are deprived of something you need to justify your belief, a Horde equivalent.
A stand-alone Alliance High Elf race is not happening as a developer would not be encouraging folks to ‘shout for races’ they want if they knew they were they coming. The decision to add them or not would have had to have been taken two or three years ago, when Midnight was chosen as the 12.0 expansion. Our developer, a senior quest designer, would have been involved with building opening quests for them and the breadcrumbs that would lead to the Alliance embassy in Stormwind. Instead, when he pressed on High Elves specifically he gave a heavily caveated answer that listed a major potential problem with them (their inability to be distinguished from a Blood Elf). Were they coming, he simply wouldn’t have answered. The very fact he responded was enough to discern they weren’t happening.
Blood Elves are High Elves, thus no changes are required. And the only acceptable alteration to Void Elves is to make more explicitly clear than they already have that some Alliance High Elves have chosen to become Void Elves. Void Elves are not a mistake you can pretend to be a High Elf on. They are Void Elves, with their own fanbase.