The prop was made for the insert, because idiot test audience teenagers were confused and now we're here discussing it.
The in-universe answer is by process of elimination, because there couldn't possibly be a Egg in that corner- means there isn't.
The cryotubes mean nothing, we've got our answer for them being the way they are, David Fincher preferred the original Alien version of the design and because of the way AlienĀ³ opens, if he had opted to go with the Aliens design he would've been saddled with them for the rest of the film.