In general, the first four years of any medical program, Allo/Osteo, are similar save the OMM training. Yes, there is a philisophical divergence between Allo/Osteo; However, it appears most, if not all, medical schools education focused on general medicine. I have yet to find a medical school that specializes in training other then general medicine; i.e. primary care. Also, I had a discussion with an MD friend of mine who indicated that the percentage of MD's who follow the FP route equals that of DO's.
During my investigation of osteo programs it seems there is a revival of OMM beyond the class and primary care. I have been informed by numerous osteo students in four different schools, and a few DO aquaintances, the use of OMM in other specialties are being reconstitued. For example, in surgery tracks, pre and post op OMM will become a standard practice again. Also in neuro tracks the respective manipulations for specific neuro pathos will be stressed again. So I think this is another reason the AOA is keeping a tight fist on its residencies. Of course, there are other reasons beyond this, but if an MD would be allowed to enter a DO residency a need for an additional year for OMM training specific for this speciality is required. Yes, this is of course if all goes as I hear from other sources.