Molybdenum: your comparison, unfortunately, is not shared by many allopathic medical institutions which, indeed, do permit the transfer of students from osteopathic programs into their own. I am aware of several schools which do allow such transfers; to name a few: Brown, Wayne State, University of Vermont (must repeat year 2, which is only a 1/2 year, after finishing 2nd year at your home D.O. school), Temple, and Creighton. Of course, the transfers are contingent upon available space, which may not be known until February or March of the year one wishes to transfer.
Institutions which do not permit transfer do not all do so because they necessarily feel that students from osteopathic schools are inferior or uncapable; on the contrary, there are some admission chairpersons whose colleagues are D.O.'s. What makes one institution allow transfer and another not is, I'm afraid, unknown to most of us. Speculation about this can and will run about, in large part fueled by uninformed statements such as yours in comparing osteopathic medical students to PhD students or podiatry students. Students attempting, for whatever reason, to transfer from an allopathic institution to an osteopathic program almost certainly will face the obstacle of not having been instructed in osteopathic manipulative treatment (OMT) and osteopathic principles and practice (OPP). In some ways, frankly, this is a more difficult transfer to propose.
I myself transferred from one osteopathic institution to another that would allow me to be closer to my spouse, and found little to no hassle in the process from either my enrolling institution or the one to which I transferred. This is, unfortunately, not the universal case, and one of my former colleagues faced considerable challenges in transferring to be near his/her spouse. Several members (approximately 6) did attempt to transfer to an allopathic institution, and one was admitted to one of the institutions mentioned above. As my former institution did not have letter grades (in favor of a pass-fail system) and did not tabulate class rank, this person's absolute rank in class was not known; however, it was widely perceived and understood that this person was within the top 5 individuals in the class and was clearly in the top 15% based on membership in the Osteopathic version of AOA (Psi Sigma Alpha).
Regarding concern over "competitive residencies" posted earlier, I echo a previous comment: your chances for getting a neurosurgery residency or cardiothoracic surgical fellowship are by no means enhanced by transferring to an allopathic institution. The odds of obtaining these types of programs are, quite frankly, slim to none for the majority of students regardless of whether one attends an allopathic vs. an osteopathic institution. Furthermore, for those who feel that they have fewer options, consider that at both osteopathic and allopathic institutions that the *majority* of graduates enter post-graduate programs which are considered 'primary care': this includes Family Medicine, Internal, Peds, and, possibly OB. Procurement of a subspecialty fellowship following completion of a residency is, likewise, a competitive process regardless of the letters after your name.