What do you mean by fully recovered and back to work?
When we say fully recovered I would expect that he is completely back to his full pre-illness athletic ability and stamina. If there is any degree of fatigue, chest or back tightness, shortness of breath, or weakness with pre-illness levels of exercise that is very concerning for diving.
Returning to diving was discussed at length post Covid. There is a big difference in potential pathology of the lungs post pneumonia vs post a simple minimally symptomatic viral resp infection.
I’m not your friends clinician, but I would have expected at a minimum a chest x-ray and possibly a CT of the chest post severe pulmonary infection before returning to diving.
As to the graded depth to the dives, I am guessing that the physician in question is basically testing how deep your friend can go without popping a bleb in the lungs due to trapped air from the pneumonia. My practice in medicine focuses on acute illness and treatment, not recovery, so I cannot comment on how appropriate this plan for diving is.
One of the other dive specific physicians hopefully can provide some more insight beyond my basic understanding.
