It's not an unreasonable assumption. There are so many prerequisites to get into med school that are hard science and math that pre meds have degrees in chemistry and biology. Of course, a history major can do the prerequisites and still have a history degree, but having seen a lot of MDs and med students in my life this is simply not the likeliest possibility. The more likely is that someone greased his skids. Ivy League, they don't follow the rules the rest of us do.
It is a cliche among people who know a lot of docs that shrinks are not the sharpest scalpel in the drawer. Sorry. He does carry the air of the smart doctor when it suits him, but I don't think he has seen many patients.