Being a defensive player is not about accumulating stats.
Being a good rebounder isn't all about getting rebounds. If you're boxing out or putting yourself out of defensive position by challenging a shot, you can't expect to get the rebound. Boxing out is a great rebounding play, but does not mean you get the rebound, it will actually help someone else get the rebound.
Some teams have many good rebounders in their lineup, so having someone average double digit rebounds is unnecessary.
Ideally, you would prefer a perimeter player get the rebound anyhow, as it allows more transition opportunities.
"If you find yourself in the majority, rethink your position" - Mark Twain