Really wasn't suggesting changing the studs, just the mounting configuration. I'm sure there's no need to do anything at this time, especially with the warranty situation. If your guy did the installation, then you would know of any use of a die.
If the Piano Man torqued the nuts, I suppose it's possible that he fractured the stud. My other thought is that as tough as studs are, the threads on the nut would have given up before the stud did.