Well, there have been enough of them that it is considered A Well Known Problem.
But then, some people never have a problem. What's up with that?
My theory is that GM got a bad batch of relays out there that didn't last, and so some people got burned.
And, since CUCVRus is known for being meticulous about maintenance, it's not surprising that he has not seen this problem.
I've done the mod myself, for the same reason that you did. But I've looked into it a lot more now, and I would not do it again. If my GP relay ever fails, I'll pull the doghead relay from under the dash and use it for my GPs (same relay) and replace the starter relay with a good quality 20 or 30 amp standard automotive relay, with insulated terminals. That circuit only draws 9 amps, so a 100 amp relay is massive overkill.
And there's also the fact that some people have had the same problem AFTER doing the doghead mod.
That makes me think the real problem lies elsewhere, and the doghead mod is masking it.