His simply saying, that if you have to appoint some value to the different skills a player might have, when it regards a guard, rebounding is not as important as other skills. So that Giddens can be an excellent rebounder, he doesn't feel that the other skills are good enough so that Giddens can rebound well is not much of a factor as it regards his NBA readyness.
This differs from from a center or powerfoward in that if they're great rebounders, usually that's a huge factor into their NBA readyness development.
I agree with this premise, but I don't agree with his conclusions.