Earlier quoted context omitted.
No, its not an edge case. If you have a rapport with a doctor/care provider, you would want to stay with them. I have a genetic disease and an endocrinologist who helps me manage it. I wouldn't want to leave that doctor, who has seen me multiple times, has my charts, understands what Im working with, and so much more.
I'm sorry but that does sound like the definition of an edge case to me. You have a rare situation that requires a unique solution.
edit: This (quite extensive and longitudinal) study would suggest that it's true. Check out the sources on the paper for other studies with similar findings: