It's easy to explain even if rebound seems the most "random" skill in BB. Reb is a skill useful for centers and they take the best % of the total rebounds. If you put your guard with lvl 1 in position of center for sure he will get more rebs than in his natural position.
1990-2022 Stalinorgel - https://www.youtube.com/watch?v=pV-Xppl6h8Et