'Independent applicants' does not only mean only IMG and DOs. That "Charting Outcomes in the Match" pdf states that anyone other than US seniors at allopathic schools are lumped as independent applicants. This would include not only DOs and IMGs but also US grads who 1) failed to match the first time around or 2) people who took a year off for a fellowship or some other reason. It is important to note as well that already-licensed physicians in other specialties who are going for another residency are lumped in the independent applicants pile.
I know my school derm program has taken on residents who have done either a fellowship year or who have already completed a residency. I don't think there are very many DOs or IMGs in allopathic residencies. The 48 you reference are more likely from one of the other categories. Someone please correct me if I'm wrong!
