Right, the feedback I'd expect in a code review interview is something like "This is unclear or wrong, write what you actually meant".

That's the feedback I would want, and it's the feedback I give to my colleagues in reviews. Actually I tend to be too verbose, so you might get a full paragraph explaining what the ISO document says and that you shouldn't assume it does whatever it is your compiler says.

My actual feelings for this specific case are that the language is defective, but if we're wedded to a defective language then the reviews need to call out such usage.

If you know is this code is bad, but don't know that it is UB, I thing you are rating code on feelings and cargo culting.