I think this is one of those cases where people don't really know what they want.
For some reason, people assume you have to be built like Kevin Love to get a lot of rebounds, while somehow forgetting that KG had a long and illustrious career while being built like a lanky string bean.
Strength is important, but overall weight is not. Furthermore, good rebounding instincts, hustle, and fundamentals (like blocking out) will beat pure size and strength EVERY time (see: Dennis Rodman, or lanky Joakim Noah).
Hell, Rondo is a great rebounder for his position and he weighs as much as a 15 year old girl.
Long story short: mobility is extremely underrated for big men in the NBA. I'd rather have you be able to run the floor to get back on defense and defend the pick and roll than get 1 or 2 more rebounds a game to pad your stats anyway.