I didn't follow his career at all, and only followed him around an exercise field once, briefly, but my understanding is that he had a "distinguished career" in medicine. I don't know whether he specialized once he began regular practice.
Some of his "theories" leaked out while he was still in training, and were discussed in locker rooms around the world, but I don't know how much of it ever got published. It did appear (viewed from the training rooms) that he was about the only one at that time who was actually measuring (mostly on himself), recording, and analyzing physiological responses1 to exercise in any way meaningful to "working hard at increasing endurance."
1 Stuff like O2 demand, CO2 buildup, amylase/acetone/ketone reduction and tolerance/effects, electrolyte depletion, etc.
Most of those trying for the 4:00 at the same time just went with "this is what I do and I'm damned good, so you should do it my way" - like the average snake oil salesman. (A couple of them actually tried to sell books on the subject.)
At the time, the only serious work within the field of "conventional medicine" seemed to be coming from the Swiss/Swedish regions, although we suspected that the Navy diving schools probably had more good stuff than they would talk (to us) about. Of course we didn't have the internet then - or for the next 30 years for most of us.