How med school differs from grad school...

Graduate school is not about classwork, it's about research. And physics is different from biology. In physics, you can think about a problem, and if you know a few principles, say, the uncertainty principle and energy conservation, you can make headway. In biology, not so much. Physics graduate school is about the forest, research is about the twigs, and medical school is about the trees, with a picture of the forest in mind.