With the offense Rose runs, there are certain positions that attempt to rebound and some that don't. I think he's been rebounding more this year because we've needed it. I don't see him in that role as often next season.
Also, you're right that 10 assists is the bigger accomplishment but when he can't count on both 10 dimes and 10 boards, that is when it is going to be harder to get the triple doubles. I still think he gets about 2 more his entire BYU career.