You're probably right... I have heard cardiac surgeons say that they like to discuss patients (longterm goals), and rub minds with cardiac intensivists who are cardiologists, because of their perspective on the outpatient stuff. No argument there.
Regarding the "plain cardiologists" comment -- I have worked with many double-boarded cardiac intensivists (3-year cardiology) who don't seem to know (or care!) about anything beyond what's basic in the neuro system, vent management, renal physiology, electrolytes, hematology, etc. I wasn't saying it to be rude, just my honest observation. It really used to make me wonder. And my conclusion was that they had gone through 2 years of PICU fellowship just "going thru the motions" with only one goal in mind - which was to eventually take care of cardiac kids. Your goal affects the way you learn, and how much attention you pay to certain things. No one ever did 2 years of PICU after 3 years cardiology - because they wanted to end up taking care of general PICU kids. None of them would want to (or be able to) care for autoimmune diseases or trauma, or even septic shock which is considered bread-and-butter in the PICU. So it's a bit of a false premise in a way. Actually some of them do part-time cardiology clinic, when not on service.