I would think it must be difficult to detect carb icing on a constant speed prop aircraft, because the governor will initially try to compensate and maintain the RPM. It should show up in airspeed eventually...
I read this in some accident reports on engine failures on twins. When doing twin training, the engine gets shut down (by the instructor) so you can see it clearly. But in reality, it often happens slowly, with the prop governor compensating and masking the problem for a while...
ALL engines should be fuel injected. Carb icing is horrid, and the need to fiddle with the carb heat is a huge distraction to safely operating the aircraft.