Fantasy films and Political Thrillers

In my last post, I mentioned "another difference" between films like Divergent and other political thrillers, and I've been trying to come up with a good way of explaining it.  Thanks to a classmate who is working on a different film (one of the Harry Potters), I have a good quotation from a source she found,  a book called Fellowship in a Ring:  A Guide for Science Fiction and Fantasy Book Groups, by librarian Neil Hollands, who says that "Some of the best political fiction written is speculative fiction.  By devising political and sociological systems in alternate worlds or by hypothesizing alternative events in our own world, authors can create a fictional laboratory in which to explore any political question" (233).  Yeah, what he said.
When I was trying to think of how to put this, I kept coming back to how Divergent and other stories like it work is by setting up a kind of closed system.  It almost makes Hollands seem to be referring to Divergent, which is, after all, about a social experiment gone bad.