that was proven false in bfa where void elves had much more presence. we saw them at the battle of lordaeron, throughout the war campaign, assaults, and even in horrific visions. actual alliance ‘high’ elves were blink and you miss them with a grand total of 4 caring enough about alliance affairs to show up
it will be proven false again in shadowlands and the next expansion after that, and after that one, etc. its only downhill from here for you guys now that alleria and the void elves are here and dalaran is officially neutral under khadgar