Certainly agreed; the book answers are that NPCs don’t gain passes and fails for advancement and don’t earn Fate o Persona.
Allow me to redirect the discussion; not do they gain this treatment, but should they gain something. I’d prefer to let the rules and rulings aside. Think of the story of the game. Are the NPCs enriched and more engaging if players know they can grow and develop (though not as rapidly as PCs) in a similar way as PCs? Could it matter to players if they know that efforts to involve their Friend or Mentor may cause those NPCs to be more capable in the future for having spent checks to get those characters engaging skills in scenes attended by PCs? What might it warn if every fight or every argument with an Enemy helps the NPC become a more fierce opponent in the future?
My initial impression is that in both cases of Friends and Enemies, it will enrich the experience and deepen the value of the NPCs when players know that drawing them into the circle of recurring characters with PCs will result in more developed NPCs. It gives much more weight to the comments by Celanawe on page 241 regarding Friends and Enemies changing their stance. If the NPC cannot make growth, why can they change? It seems to me the story begs for NPCs who both grow and change over the course of a campaign (if they are frequently present and making use of skills in serious tests).
I am pleased that I’ve got a method of pulling together BIGs for an NPC who I plan to use in a session. It really helps out. I find myself too often displaying the opposite weakness–I have NPCs too stubborn and ingrained to be manipulated! When I give them a Belief and Goal, I find it easier to let them be influenced. I know that anything outside the Belief or Goal isn’t worth a conflict (though a versus test may still be appropo). That which falls in the umbrella of the Belief or the session Goal is immediately a candidate for conflict.
It helps me especially to sort out how much an NPC really needs spotlighting. If the patrol mice are not stomping on the Belief, the NPC doesn’t need to be a showcase. If the patrol won’t create a barrier to the Goal, the NPC doesn’t need to be an opponent. I’ve found this helps to reduce the number of tests I’m anxious to falsely create over an NPC.
In a particular example, I had brought an Enemy interested in the romantic rivalry between himself and a patrol member (a Tenderpaw, in fact) over this Guard’s betrothed. Since that was the entire circle of his Belief and Goal for inclusion, it was easy to ‘say yes’ when another patrol member wanted to speak with him alone in an effort to avoid a fatal duel–his goal was nothing to do with killing, only humiliation. However, later in the Player’s Turn, the patrol mate had to test to put his lights out and leave him unconscious in a boat under a tarp.