Whether the user did anything wrong or not, a couple isolated incidents should not cause any concern. The defect rate of CPUs or motherboard is never zero.
Unlike the 7800X3D problem, that came to light shortly after launch, these CPUs have been in wide use for like 3 months. That's more than enough time for any sort of systemic issue like this to surface. So, either something happened with this user's CPU or motherboard (possibly during installation, possibly during production) or he just got unlucky and received either a rare defective CPU or mobo.
I am a little uncomfortable with some of the narratives around the owner. I think we should try to give him the benefit of the doubt and assume his story is probably accurate (while still allowing for the possibility that it's not).