There’s an inferred lore explanation for that as well. The Sunwell is, basically, all Titan blood, pure Arcane, ergo it emits the same sort of radiation that changed the Dark Trolls into Night Elves, and made them resemble Titans more (smaller fangs, more delicate features, smaller build, etc). The High Elves were tied more closely to the Sunwell than the Night Elves were to the Well of Eternity, it seems, and there wasn’t any influence from Elune at that point. So they changed to resemble humans more so because humans=Titans.
Or you could just go with the theory that elves in general have the genetic stability of rubber bands and change their entire aesthetic based on what brand of coffee they drank that morning. Either one works.