I think the OP basically confirmed this above, when he was talking to the service rep.
beside the troubleshooting steps and / or information you provided to the technical agents, our Warranty Return Center only validate the markings on the unit when it is received. We do not perform any test of the faulty units.
That said, I think the k-series CPUs should have a warranty separate from the locked proc warranties. I don't think it necessarily needs to be anything drastic, but something that would encourage the purchase of them over locked CPUs. Perhaps extending the boundaries of the warranty to some Intel-determined 'safe' voltage limits, as well as other defining other 'safe' protocols (allowing the usage of aftermarket coolers, etc).
But business is business, and I guess enthusiasts will buy the CPUs either way it goes.