I think rankings are wacky because juco's are more unpredictable than the top-level high school guys who play on high-level AAU teams and can be scouted and evaluated more easily. Plus they need to contribute right away to have been a "successful" recruit.
Read something but now can't find it, so recreated it myself. The following is the top 10 juco's from the 2014 class (247 Sports) and their ranking, along with how they did the following season at the school they signed at:
1. Cinmeon Bowers (4 star/96). Auburn. 30 minutes/12 points/10 rebounds
2. Kadeem Allen (4 star/93). Arizona. Red shirted/did not play.
3. Jordan Goodman (4 star/92). New Mexico. 19 minutes/13 points/6 rebounds.
4. Torian Graham (4 star/92). Houston, then Buffalo, ate marijuana at traffic stop-now ASU. Did not play LY.
5. Shane Henry (3 star/91). Va Tech. 10 minutes/2 points/3 rebounds.
6. Stephen Hurt (3 star/91). Kansas State. 13 minutes/4 points/3 rebounds.
7. Trahson Burrell (3 star/91). Memphis. 23 minutes/9 points/5 rebounds.
8. Willie Atwood (3 star/91). Arizona State. 11 minutes/3 points/2 rebounds.
9. Trey Dickerson (3 star/90). Iowa. Played minimally and left program.
10. Michael Chandler (3 star/90). Oregon. 5 minutes/2 points/1 rebound.
For perspective, Malou is a 4 star/93, ranked #2. Jackson is a 3 star/91 and ranked #7. This is a small sample, but the results are pretty consistent year-to-year.