I will maintain that, unless an additional story is made set between Aliens and Alien 3, the most logical theory, having ruled out most of the popular theories with conflicting factors presented on screen, and using what we know about the alien (and a little of what we don't know) is that the eggs grew there. It's the only theory I think I'd be happy with accepting as plausible at this stage, taking into account the egg/eggs position, the black resin dripping down from above around it, the fact the prop has a smaller unformed egg next to the cluster (suggesting that was the mindset) It grew. Eggmorphing hasn't been expanded upon enough... we assume the host is changing into an egg, but it could just as easily be the case that the host is feeding the growing egg nutrients in the first movie; it may aid maturity but may not be needed. Big chap certainly didn't lay full sized ovomorphs, and the queen doesn't have "emergency eggs" when we clearly see unformed 'yolks' pouring from her egg sack when Ripley launches grenades at it. It's impossible for it to be Bishop, and for arguments sake, if it were, it'd be in a secure hold for transport to WeYu labs, not randomly placed under flooring upside down and covered in secretions.
A cluster of growing eggs is the only logical assumption (in something that we as an audience know doesn't make sense, was simply a studio demand... but it's what we are presented with, it's on-screen so it happened). The fact that we saw dripping acid burning into the floor by Bishops feet from her wounds from losing the eggsack (and you would assume this leakage would continue through the fight with Ripley in the power loader) *and* the fact the location of the egg bares a striking resemblance to the underfloor area Newt was crawling in just helps lean into this.
I feel the "it was all a dream in cryo, there were no eggs" is too lazy, and also presents the problem of how a facehugger (or huggers) got on board - they clearly didn't hitch a ride on the Queen (we saw the Queen multiple times before it got on board the dropship).