Just checking in to add my regular 6-monthly reminder that the most logical explanation is simply that there is a story between Aliens and Alien 3 that we haven't seen yet. This is why everyone is now in a different cryosleep room, and will explain why there were xenos on board the Sulaco. No 'emergency egg', no 'Queen stinging Bishop', no egg morphing, no walking eggs, no Bishop miraculously finding the time to get two eggs and sneak them on board then for unknown reasons planting them in an unlikely position... Just simple events between movies, another encounter.
Until next time...