The best rebounders aren't tall guys. A lot of good and great rebounders have been under 7'0. Buck Williams, Charles Oakley, Elvin Hayes, Bill Russell, Jerry Lucas, Charles Barkley.
For example, Gheorge Muresan standing at 7'7, during his best rebounding year ever, averaged only 15.6 rebounds per 48 minutes. Dennis Rodman, standing a foot shorter, averaged 22.5 rebounds per 48 minutes in his best rebounding season.
Using the calculation of per 48 is being generous to Muresan, because it doesn't take into factor his horrible stamina that limited him to 11 less minutes per game. It also benefits the guy who plays less minutes, because it is easier to put up number in a small part of the game than playing close to the full game and getting tired. This is why you will see a lot of inflated stats when using PP48.
Using per game stats, or even per 36 minutes, Rodman almost doubles Gheorge.
Another giant, Manute Bol, never bested his rookie mark of 6 rebounds per game.
While 6'5 Elgin Baylor averaged nearly 20 in his best season.
This can also be applied to modern NBA, with Howard, Blair, Millsap(especially Millsap, dude is a monster at his size) being much better rebounders than Nowitsky, Yao, Ilgauskus.
Height is more essential for blocked shots, but in certain cases even that isn't true, because the giants are often clumsy and cannot jump or have poor timing.(Shawn Bradley)
Athletes like Mourning, Howard, even little guys like Wade and not really a little guy but little in terms of this discussion Jordan blocked a lot of shots despite their size.