We've seen how most of these Allied Races have played out so far: take existing player races and tweak them. As a developer, it's just much easier than creating entirely new player models from scratch. So we get Nightborne that look a little too similar to Night Elves even though the NPC assets were already in game. Apparently, it's just much more feasible to move one player race to another.
Battle for Azeroth is coming, and the focus is on Zandalar and Kul Tiras. Horde and Alliance need to make allies with these new islands. It is confirmed that the Horde will get the Zandalari Trolls for an Allied Race, and for the same of argument, I will assume Kul'Tiras humans will join the Alliance in time.
Why did they make the Kul'Tirans the "fat humans" the message boards are irritated with? Why not use the existing human model and give it some flair, like the Highmountain and Lightforged Allied Races. Why go through all the trouble to make completely new models for an Allied Race of this stature and giant size? I have to conclude that they plan to reuse these models for another Allied Race in the future. And what race do we know of that the players have wished for for over a decade that are essentially "fat humans"?
It makes complete sense that these models were created not only to give the Alliance some body diversity, but with the intention to reuse them for Ogres in the future. Look at these images for an idea of how simple it would be; and perhaps we have a glimpse into future female Ogres as well!