It's true. That's why, when one is breaking down minutes distribution, it's always wiser to look at minutes over 82 games, rather than over one game.
So, if we give 48 minutes for each guard spot and, say, 12 for the 3... that's 108 minutes in a game between four guys. That's 27 minutes a game for each of the four guys.
But over 82 games, that is 8856 minutes... even without significant injuries, guys are going to miss five or six games a year. So if we divide 8856 by 304 (4*76, where 82-6=76) that's up to 29 minutes a game, and that's a pretty conservative average.
The Blazers shouldn't have to rely on guards like Skylar Mays and Tony Snell as starters at any point of the season like we have the last couple of years.