When I say it concerns me, I didn't mean I was frightened or thought I couldn't handle it, just that it could be a fright for the student.
Also thinking about inadvertent spins in a type not cleared for intentional spins, and the outcome being a very steep spiral. Recovery is simple enough, but I'd imagine it would be very easy to pull too hard and over stress something.
I am confident and trained in spinning and basic aerobatics, I've never had an engine stop but I have spoken to a few people who say it stops almost every time they spin. I'm just wondering what they are doing to cause this since I have not experienced it myself. The advice I had from my aerobatics instructor was to pick your field before you start the maneuvers just in case.