While many of us are presenting our opinion based on story and lore, youāre asking your question based on in-game models.
Thatās why Gilnean Human (worgen cursed) and big beefy strongmen from Kul Tiras are added as a variation of CORE HUMAN RACE, thus Allied Race.
The playable Kul Tiran have different customization than other 2 human races. But weāre speaking only about playable Kul Tirans. All over Kul Tiras you can see normal human models (cough - Derek, Katherine, Jaina) or skinny Kul Tirans (which are not part of customization option).
The present Kul Tirans settled in Kul Tiras like 2000+ years ago.
The thing is, what youāre pointing out, are the playable models. Yes, but also no - theyāre the same humans as Stormwind ones. Blizz can literally add Kul Tiran model as customization to core race Humans - because the Kul Tiran model is just one variation how do Humans look in game (btw. they made them bulkier and stronger to reflect their naval culture).
Kul Tiran, OG Humans and Gilenan (hell even the Forsaken) are all Human Race, with distinct models and visuals. Theyāre not different race, they have only different variations.
Are Quelādorei or Sinādorei distinct in any way? Blue eyes? Is Vereesa or Alleria looking different than Liadrin? Is Halduron looking different than Romath? - If your previous statement should be followed, then all new added High Elven People should be visually distinct from their Sinādorei brethren (new models, and totally different customization). Is it what HE fanatics want? - No! They want exact same copy with new name and itās only matter of time when theyāll start screaming that Silvermoon should be Alliance and Sinādorei should pack and sail off to Orgrimmar.
What you want in High Elves is the same as if anyone else was asking for Shenādralar as allied race - same model as Kaldorei but different name. That would be adding same race twice.
LF Draenei vs Draenei - we have clear evidence why theyāre as playable allied race - infused with Light - not sharing any customization, racial, mounts with Draenei.
Blood Elves were not infused with fel to the point, it would make them so distinct from High Elves, so they should be considered as different race.
Do you consider Human from Stormwind to be different race as the Human who survied Lordareon or Humans from Stromgarde?