Simon150, looks like you're talking about practical flying. I mistook yours is a pure theory course.
Agree with your analysis - in order to pull a max rate turn, the stall speed is much higher and Va is close to the mark for the average training aircraft anyway. I also note you are referring to a max rate turn rather than a max rate level turn, so the descent does the trick.
In a min radius turn, you're going to have the same problem because you need to build up speed to avoid the stall in the turn.
Is there really a practical difference between max rate turn and min radius turn then ?