All the other 11 immune people being just npc's is the subversion of expecations that happened throughout the whole season, is john cena explaining the hdp.

First episode makes you think they gonna be the avengers assembled just to turn that on it's head by the next episode.

...and then we see what is clearly corpse bags at the end.

I don't think it was a "character knowing before the audience" moment at all; is was just about putting the puzzle pieces togethef

Already in episode 2 we see them putting corpses in the back of a milk truck, we see the trucks many times in ABQ, and the crows and wolves references on top of it, etc

Is pretty obvious which movie it is, you even have an unique character's name in it