Why do certain parts for the VQ37 engine fit the G37 coupe, but not the G37 sedan?

I somewhat understand why certain headers could fit the coupe and not the sedan, but I was looking at a Jun 72 Camshaft and from what I see, it'll only fit the coupe. Does anyone know why? From my understanding, they have the same exact engine. via /r/cars http://ift.tt/2sNBQhV