I would agree with the above: yes and no. I wouldn't base AD chances off of CULP, however CULP uses similar criteria (albeit much less, so GPA factors much more). And other times, people simply aren't chosen despite their quality, much like the stats JCleppe pointed out. Usually the upper echelon of MS1's and MS2's apply for CULP and the upper echelon of those are usually selected. The entire cohort is strong, but there are limited slots.
Funny story, I actually wasn't chosen for CULP my MS2 year despite being a fairly strong candidate while another guy from my school with much lower stats was. (Even though I later went on 4 CULP trips as an MS5, lol) he's now in the Guard (not by choice), and I'm active duty. Hopefully, that reassures you.
And if he wasn't chosen, reapply next year. MS2's may be the priority for CULP, but I've seen 1's, 2's, 3's, 4's, and 5's on CULP. Just have to make the schedules work. CULP is one of the best experiences you can do in ROTC, just behind CTLT or an internship.