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.
And a movie has never been changed in post before.
There are also the reports of a version screened without that scene in it.
I think they are making it up as they go, if they change the race they change the race. People are giving this production way more credit then it deserves so far. There is a reason they have done multiple test screens and that is because they are still searching for the story they want to tell in the footage they have.
Said it elsewhere, i think at some point it was engineers, if it still is when we all go to the theatre remains to be seen.