There's a familiar pose in watch circles: the man who's "moved past" collecting and now wears one perfect piece, usually something quietly expensive, and lets you know it's the only watch he needs. It gets treated as the enlightened endpoint, the maturity the rest of us are supposed to reach. I think it's the opposite. It's the loudest flex available, laundered through the language of restraint.
A guy with a tray of affordable watches he rotates for fun is just enjoying a hobby. The one-watch minimalist has spent the same money or more concentrating it into a single object he can point to as proof he's beyond caring, which is a strange amount of caring. "I only need one" only lands as a statement when the one costs enough to make the line worth saying. Nobody announces their single quartz Casio as a philosophy.
Restraint that needs an audience isn't restraint, it's a more efficient delivery system for the same status signal. The collector at least admits he's playing. The one-watch sage is playing too, and pretending the game is beneath him is part of the move.