Obviously there's no way to measure this claim besides the eye test, but the guy has a legit skill level at diving after balls the likes of which I've never seen. Some guys will dive after a ball to show some hustle and others might even get to the ball, but for the most part you're looking at a timeout or a jump ball if they do manage to get it. Marcus not only has the will to go to the floor, he has the uncanny ability to cut down the angle of the other pursuer (who is often closer to the ball) and position himself to not only get the ball, but secure possession by getting it to an upright teammate (often before he hits the ground). It's more than just the desire to show hustle.
It reminds of Rodman going after a long rebound. He would know which way the ball going to go for before it hit the rim and beat everyone there. Definitely a unique skill set, and good for a possession or two a game (we'll leave the other side of the possession out of the conversation).