It’s not really about self absorption, for a lot of people it’s a way to track progress and feel proud of themselves. Sure doing it when people are changing/ pissing is not good etiquette but in the context that OP was using, he was just trying to put down a random dude he was jealous of.

Yeah idk man this just seems really obsessive not going to lie. And putting down a “gym bro” for flexing in the mirror is a bit cringe. I wish you luck on your crush but focus on yourself in the main.