One of the scenes that shows the importance of the narrator is when Pitou uses Dr. Blythe to stall herself in the air. Because she's the only one of the three royal guards incapable of flight, she had no choice but to wait until she landed. She's able to keep her head straight and use En to properly survey the situation, something Pouf isn't able to do because he panicked and because he was able to act as the palace was bombed. Thus she was the first of the royal guards to find the King, and that's why the arc went down the way it did. The narration's needed because the arc is shaped by decisions the characters make, based on their knowledge of the situation and their own personal biases. Otherwise you would just have everyone internally monologuing why they feel a certain way, which I'd argue is more intrusive than a narrator. Sure some of the exposition isn't necessary, but quite a few times during the invasion a character makes an incorrect deduction, and narration is the easiest way to explain what lead to their misunderstanding and how they arrived at that conclusion.