The rule is there for a reason. I think this is an easy ask of the coach why he's not getting that. Our rec soccer league has a clear 50% at least playing time.
It's one thing to be playing on the actual competitive high school team where you're playing to win, but rec and, IMO, younger youth sports are about getting everyone experience and having fun first over the winning. Leagues that have minimum plays or playing time are saying that all kids should be getting game experience (unless there's behavioral problems to warrant less).