I didn’t say that they never spent a few years in learning. I said that they made most of their kinyan torah while working. I.e. a 65 year old man who matches the description you suggest, but is now a retired actuary living in flatbush. Are you going to tell me that everything from the time he turned twenty-one was just chazara? (These details aren’t made up out of my head. I’m talking about someone in particular.) Obviously someone who plans on being toraso umnaso has to take it at least as seriously as any other umnos, but you can become a talmid chochom –not rosh yeshiva level, but a talmid chochom nonetheless — learning part time.
As for your moshol, I once worked with a guy who was doing just that, except it was two phd’s in completely different fields instead of law school and an MD. At the same time, some of our coworkers were in medical school while going for a phd in some other science.