The easy cases like you cite are also those that don’t cause problems in practice. I’m not sure that would help all that much, other than to slightly reduce internet criticism.
The issue is that the list is infinite (anything not specified is UB), so actually removing any finite amount of UB from the list won't make it shorter.
(only slightly tongue-in-cheek, I do believe that removing silly things is worthwhile).
To be undefined behaviour, it must at least be valid syntax. The syntax is described in a finite document. Also it only gets executed by a finite machine, that has a finite number of finite descriptive documents.
And it also signals that you actually do want to improve, just a little bit of boy scout rule goes a long way.