I can’t recall where I read the song was about Phil, but it fits pretty well.
He was easy-going, smiling, friendly & laid back compared to the uptight Charterhouse boys. He was amused when he watched them have screaming rows & storm off over some minor musical point. He passed the audition by listening to other drummers from the swimming pool. And given his hair & beard in his early Genesis days, no one can deny that “Someone says he’s Jesus Christ” was a good description!
The “nun with a gun” line is a mystery but perhaps it referred to some contemporary event/film/song?
But you actually read somewhere it's about him?! Dahhh.... that's kind of put me off it a bit now! I don't like songs being so nailed-down like that. I preferred thinking of it as a generalised thing about someone who doesn't care about anything, and the 'nun' and 'fool' lines were just a throw-away oddity. Grrrr.
In fact I'm going to carry on thinking that, and pretend this whole exchange never took place.
This is like when I read that Who Dunnit was meant to be a dig at punk, embarrassingly 4 years too late, and that Cul de Sac was about the sodding dinosaurs, for crying out loud. Sometimes I think I should just stop reading things.