Based on the types of shots each team forced (in terms of location), the expected outcome of those shots (defensive/offensive rebound), and a teams actual defensive rebounding rate (DRR), we are able to determine which teams are over/under rebounding. If the shot locations say you should be rebounding under the league average (DRR), but you are above, your team has skilled rebounders. The opposite is also true. Here's a table breaking down which teams rebounded under/over their expected rate, and therefore, which teams possess "skilled" rebounders.
*It goes from least skilled to most skilled.
Blue=Not skilled Yellow=Average Red=Skilled
On the flip side, teams like the Bulls, Lakers, and Sixers don't have high rebounding rates because they are skilled, but because of the type of defense they play. They force a lot of long two pointers at low percentages, which translates into few offensive rebounding opportunities for the other team.
Hopefully this post can help clear up some murky thoughts regarding rebounding. Defensive rebounds are in part (30%) due to the type of defense your team plays. However, as this table illustrates, having skilled rebounders is even more important then forcing the opposition into "bad" shots. The blue group tends to force a large amount of shots that should turn into defensive rebounds, but don't recover them nearly as much as they should.
In contrast, the red group forces shots that usually end up as offensive rebounds, but still manage to turn a large amount into defensive rebounds.
That's it for now. I'll probably start on the relation of shot locations and offensive rebounding, as well as determine how consistent these trends ore from year to year.