OK, if you are fundamenting your assumption on the first Alien... but this was a different Alien, who preferred killing to nesting, so to speak...he killed Clemens and then carried his body away, he killed Spt. Andrews and most, if not all, of the prisoners, so why and when would he be nesting...? It would require living hosts to breed (Dallas was alive in the nest) so why kill ALL of the prisoners/potential hosts for the Queen which it knew was about to be born...? That is why I think this Alien was not a drone alien (not the abandoned white alien concept from James Cameron, but the ones without the dome) but a warrior, meaning it was there to protect the Queen, and eliminate any potential threat to it (prisoners), that is why I think he was not nesting, we sticked close to Ripley and the prisoners because it was required to do so, being the Queen's 'bodyguard'... The Superfacehugger had two embryos, one queen and one warrior, which implies that this Alien's mission was to protect the Queen at all costs, eliminationg any threat and not coccooning or nesting... At least, that is my take...