The models were also low poly count trash back in the day as WoW tried to go off what models existed in Warcraft. That don’t mean that is part of the lore. As Garrosh says “Times change”. A highly requested change is that Worgen be given an optional tail, upright stance for males, lore correct size and so on. Its simply character customization that gives players more looks to make their character unique.
P.S. Even the female troll model got changed and updated. You ever see the old model?