Two things come to mind...
First... does it matter if NPC's are or are not PF members? Does this have any bearing on gameplay at all?
Secondly, perhaps the thinking is all wrong.
Perhaps NPC's are not PF members, but are still rated by the PF, thus they have combat ratings, much like movies and television shows are assigned ratings or even video games are assigned ratings by an organization that the television, movie or game industry is not a "member" of, and in fact would probably be much happier if these ratings industries did not even exist, but that is a subject for a different discussion on a different forum.
First... does it matter if NPC's are or are not PF members? Does this have any bearing on gameplay at all?
Secondly, perhaps the thinking is all wrong.
Perhaps NPC's are not PF members, but are still rated by the PF, thus they have combat ratings, much like movies and television shows are assigned ratings or even video games are assigned ratings by an organization that the television, movie or game industry is not a "member" of, and in fact would probably be much happier if these ratings industries did not even exist, but that is a subject for a different discussion on a different forum.