Author here

> The part about hardware is wrong BTW

Could you be more specific? I think by "wrong" you may mean "not actually relevant to UB", and you're right about that. If that's what you mean then that part is not for you. It's for the "but it's demonstrably fine" crowd.

> the hardware semantics are clearly defined

Yup. The article means to dive from the C abstract machine to illustrate how your defined intentions (in your head), written as UB C, get translated into defined hardware behavior that you did not intend.

I'm not saying the CPU has UB, and I wonder what part made you think I did.

That's what I mean game of telephone. The UB parts get interpreted as real instructions by the hardware, and it will definitely do those things. But what are those things? It's not the things you intended, and any "common sense" reading of the C code is irrelevant, because the C representation of your intentions were UB.