Roles are slightly different. Cardio and Gastro physicians undergo training in the real of internal medicine before specialising in their respective procedural-based specialities (stenting, scoping, EP). So they have the capacity and the skill set to manage common conditions that a surgeon would be very rusty at practicing (since they dedicate so many hours to surgical training and don't have the official internal medicine training). however surgeons can be good at internal medicine, especially the bright ones (like A.Kow).

However this does make a difference especially in private practice. For example, a cardiologist can manage hypertension, HLD, basic diabetes and so can a gastroenterologist. They essentially are more confident in GP work. So the base revenue of a private clinic would be clinical practice, anything on top of that like scoping, stenting, are bonuses. (esp. for stenting, most are non-emergency)

But for surgeons they have much fewer "clinical" patients and much lesser "GP" work. Of course there are those specialties like ENT, Plastics that have a "clinical" side to it- ENT has management of common ENT conditions like OSA, AR, and OM and a whole lot of nasoendoscopes, and plastics has the 'aesthetics' side to it.