I've had carb icing on the ground FREQUENTLY in the R22!
It's fairly common on the first flight of the day to find that when you check the carb heat the RPM drops, then rises a LOT as the carb ice melts...sometimes enough that you have to reduce the throttle to prevent an overspeed.
I've also had the engine stop due to carb icing , on the ground, in both a C150 and an R22. In the C150 I'd been out with a safety pilot as I was a bit rusty, came back to let him out, and was about to go flying. I had to wait ages to taxi, the engine started rough running, I closed the throttle (no idea why!) , and it stopped!!! I refused to fly the aircraft, until an instructor assured me it was carb icing. Apparently the position of the carb in the C150 is different from that of the C152 which I usually flew, making it more exposed and more prone to carb icing. So now I use that carb heat little but very often!
In the R22, we'd been out flying, on a day I would have thought was too cold for carb icing - temp below zero and cold and dry. I was shutting down, closed the throttle, and the engine stopped.
Again, I was assured by a multi-thousand hour instructor (since I wouldn't believe it from anyone else) that it was carb icing.
That's why I repeat what I said...in this country carb icing is possible in almost any conditions, and frequent 30 second blasts of carb heat when you don't need full power are not going to do any harm, and could do a great deal of good.
I know there's already more in the PPL syllabus than most students can cope with, but perhaps we need more emphasis on when and why you get carb icing, and less insistence on exactly where in the circuit you put it on and off, with instructor A insisting instructor B's way is wrong etc etc. I spend years with an incomplete knowledge of how it all worked (not saying I know it all now, by any means), and I'm sure I'm not the only one.