K series cranks=weak?

A friend of mine was at the nopi race in dallas with his all motor car and noticed Norris(K powered insight) broke often.He mentioned that it was crank realted and that the crank was twisting with that much rpm.Im not sure as too how much truth is in this,as I have been working with K motors since 2002 and they seem to be much stouter in every area than the B engines.But also mentioned to me about about the crank skunk was running and that they rarely ever break.
Question is,are the K series crank weak when it comes to high rpm?Ive never taken one that high with as much power as Norris put's out.