depends what they did. Often after recurrent pneumothorax they will put a sclerosing agent in to remove the potential space between the lung and the chest wall. This removes the potential for a space for air to move into and so removes the chance for pneumothorax. If this is the case and I assume you have had some follow up with respirologist and or thoracic surgeon and appropriate imaging than your doctors reasoning may be correct. I would add though that if it is mechanical you should be able to reproduce the pain with simple deep breathing exercises. If putting out similar efforts in the flats you don't get pain I would think it is more positional though.
I would also have concerns regarding cardiac status depending on age and other factors.
I am an asthmatic and certainly get some pain in the chest when spending far too much time in the red zone, which certainly would include most climbs with all those damn skinny bike racing elfs. Never attributed it to my asthma, just to the usual suffering of the sport that I love.
My case is exactly coincide with your said. My first surgery was for autotherapy, just made a hole and put pipe into my chest. but pneumothorax a relapse, then the doctors had treated exactly as you said. after healed from pneumothorax, asthma was came.
I agree about damn skinny bike racing elfs. lol. They just torture as mentally at the climb.
In anyway, I might be adapting this pain myself. I'm gonna try to like suffer as you, even it's to hard to patient.
Thanks for your advise.