Mike: your last two para's: absolutely correct.
Most Lycomings have the intake pipes passing through the oil sump, which does warm the intake air quite a lot (unfortunately, this might not help icing upstream of this position, but it does explain some way towards the "carb heat to cold on final" instructional policy on C152, Pa28 and C172..0-300 excepted).
One of the problems is that many Instructors do not recognise this (potentially life-changing) difference with the little old Continentals, and are inadvertently conducting conversions to type for new owners (particularly with the newer requirement for "differences" training) and could be leading owners to applying their C152-training methods to Luscombes, Cubs, Aeroncas, Taylorcrafts, et al. I think VW's are prone to the same? But my experience of these is small.
Regarding accelerator pumps, you are again correct. Fortunately in these circumstances and in my experience, both the Instructor and student only need the thing to stop once for them to learn the lesson...and generally the result is reapplication of power in the appropraite manner...but Carb Ice is so variable and insidious, it is a different matter that might catch out the unaware at any time.
Well there we are. I think that's the limit of my knowledge and experience, non instructor, just a ppl (and I'm slightly at a loss regard your venturi bit, but perhaps for another topic).
Welshflyer: I had the same in my old mini Clubman a few decades ago; it had a "winter" setting for the carb to prevent this, basically a permanent hot air source during the colder months.