IIRC, the synopsis indicates it is the Engineer homeworld as does various other press.
I think people are clinging to the rather flimsy fan theory that it is some random other planet with some heretofore unseen race of aliens never before seen or alluded to in this franchise simply because the idea that David ups and nukes the space jockeys for lulz seems lazy and abrupt. Which it is. But I am 95% sure that is exactly what has happened, just as every leak has borne out and just as the Cinemacon footage bears out.
Also, the bodies are only 'diminutive' when they're half-sunken into the earth.