It is a bit of a stretch. However, we are officially and literally the worst offensive rebounding NBA team in history. How many KG put-backs have you seen in the last three years? It appears that Rondo called this spot on, and KG acknowledged him.
Maybe an expert will set me straight, but it seems logical that we'd be terrible offensive rebounding. I think it starts with Rondo. Rondo can't shoot. He's a horrible shooter. It's established. Downright terrible. He can hit shots 2 feet from the basket and beyond that he's a liability. So our offense is built around that. Ray spreads the floor and keeps defenders on him. Pierce is a dynamic scorer who always needs attention. Then you have both KG and Bass whose offense relies on mid-range jumpers. Why mid-range jumpers?... because it keeps the opposing team's bigs out of the paint on defense... allowing Rondo to penetrate inside and hit shots within his range (2 feet from the basket). Because our team has no low post presence (somewhat intentionally), we rarely have bigs in rebounding position. They are too busy floating around mid-range giving Rondo assist opportunities and giving Rondo room to penetrate inside. It's also PART of the reason Rondo has such inflated rebound numbers for a guard... a lot of balls just bounce to him and he happens to be the one in best position to get it.
That said, we're also just an undersized team in general and often our best chance of getting rebounds (even on defense) is to let our default "bigs" box out and hope the ball bounces to the right guy (often Rondo). If we had a big man rebounding leaper like Dwight HOward, I think things would be different... but then you'd probably need a better shooter than Rondo... otherwise defenders would just plug in the paint (Dwight has can't hit mid range) and it would give Rondo less space to make layups.