Hmmm. I am reading this differently. From p. 34, "Once all players have had a chance to narrate their character's actions, the turn ends and a new turn begins." I interpret that as:
A Turn is a set of Narrations, beginning with the GM's and ending with the last player's
So, at a table with 4 players and a GM, if everyone plays a Plot Point on their Narration, by the end of the Turn, the GM has 4 Plot Points (he spent his one, but gained 4). The next turn, if everyone plays a Plot Point on their Narration, by the end of the Turn, the GM has 7 Plot Points (he had 4, spent one, gained 4). This obviously escalates if players play more Plot Points than one per turn (as they can), and it subsides if they stop playing Plot Points.
So it sounds like you advocate the GM playing more than 1 Plot Point per turn; you allow playing 1 Plot Point per Narration? How has that been working for you?