I think all skills are used based on the position played and the tactics used. Your guards probably contribute a little bit of inside defense, and your center a little bit of outside defense. The small forward probably gives a little more ID when playing a 2-3 and and a little more OD when playing 3-2.
Rebounding may not vary as much by position as other skills, though your guards won't get too many offensive rebounds. My guards had 37 TR, but only 6 OR, while my forwards and centers had 117 TR and 32 OR. 37/154 is 24%, certainly less than 2/5 (40%), but not like they don't get some. 6/38 of OR is 16%, but you wouldn't expect your guards to be battling underneath since they're going to have to get back on defense if the other team gets the rebound.