You're forgetting that we have 3 semesters/year here for a total of 10 semesters, equalling 3 years and 4 months of school when we graduate. 7 semesters (2 years 4 months) on island and 3 semesters (1 year) in clinics. So there are students from 3 different semesters that add up to the entire class of '18 from Ross. We all walk at the same graduation but get our diplomas at different times throughout the year based on when we finish clinics. So for me, I started in May '15, I will start clinics in Sept '17, will walk at the annual graduation in May '18, and will "technically" graduate and get my diploma in Sept '18. When I walk at graduation I will be walking with my whole semester, as well as the semester that started before us (started Jan '15, technical graduation date May '18) and the semester after us (started Sept '15, technical graduation date Dec '18).
How clinics works for us is totally dependent upon the school we end up at so I can't comment on that too much but if you're seeing Rossie names in rotations that aren't usually for new babies they could definitely have been from the groups that started in Jan, last Sept, or last May.
If you have any commentary about your clinics experience let me know! I have to put my selection of 4 choices for where to go on May 8th. Right now my priorities are to go somewhere that I can leave and be hired without my new employer having to hold my hand for every little thing, get some hands on exotic pocket pets (mostly I care about sugar gliders, no real interest in wildlife or zoo), and cheap cost of living!
ETA: Totally didn't even read your last two sentences! They hold our graduation in Florida and we graduate with our fellow Rossies, which will be an awesome reunion but bittersweet I am sure because we will feel like we are missing out on that experience with the new friends we have made at clinics.