I actually believe, it's not the engineer homeworld and the Scorpionaut was deliberately left there.
And there probably was one on earth too, before they revolted.
Everyone there looks so... in awe to see the Derelict like "it's coming back" after such a long time.
And if I was to guess again, I would suspect that David has "learnt" what the Engineers are doing / all about
And it has something to do about weaponizing this black goo.
Engineer creates life, black goo-ed it, but then for which purpose, I'm sure it's what covenant is going to set, so we understand there's something "bigger" than just a robot killing all engineers and creating the Alien (it doesn't sound very Scott's like to be honest, it lacks depth).
Also, if you take a very very very close look at the pictures and promo videos, it's very very very very very very very very (I can't put enough very) obvious, that this "round plaza" thing IS A TRAP.
It looks so well designed to weaponize the black goo, there are even fences that closes on the entrance to trap everyone.
It can't be there just by "accident" or "randomness".