I dont see how being the best rebounder in the league is no impact
If hed just consistently apply himself on D and take what he can on offense.....
It's about how/when the stats are being accumulated. For rebounding it could be things like, not being in proper position on either end of the floor because he's to busy trying position himself to get the rebound instead of, for example, boxing a couple of guys out so a teammate can get the rebound.
It's like when Westbrook won the MVP for averaging a triple double...all of those triple doubles he had, didn't really have a lot of impact on winning. A lot of them were just empty stats, (scoring inefficiently, teammates going out of their way to make sure he gets rebounds, staying in during blowouts, etc.).
If Drummond comes in and understands that he's going to be sacrificing stats for a chance at a title, he'll find that he'll have fewer stats, but the stats that he does have, will have a direct impact on winning.