it was a success, it didnt run away, he climbed back in and taxiied off,in my aircraft were two atpl holders, 30,000 hours plus between us, both senior instructors, one a caa panel examiner, both shaking our heads,, its all about risk management, just because you get away with a particular technique doesnt make it the right one.
I once saw a successful swing start on a tiger moth , where the throttles were accidentally left fully open, flipped over and was destroyed.