evan1975 said:

Them being humans in a costume is a minor disappointment for me. If they had done something mindblowing with the concept I wouldn't mind the retcon, but they didn't.

Ultimately, making the Space Jockey into man's creator makes the Alien universe smaller.

I'm not even completely sure if Engineers = Space Jockey. The Space Jockey looked like it was 20 feet tall and the Engineer looked half that, at most.

I'm guessing they want the Space Jockey from Alien to be some kind of "head engineer". That could explain the size difference. But, I think it would have been better to distinguish the concept of Engineers from the visuals of the SJ.