BYU gets most of its rebounds from opponent misses. Opponents shoot 34.4%, 10th lowest nationally, so BYU gets a ton of rebound opportunities due to our tempo (because BYU tends to dictate tempo to lesser opponents) and their bricklaying.
Offensively, BYU is 21st in FGA per game and their opponents have attempted exactly the same number of shots BYU has (331), so I believe that ties everything up neatly in a little bow.