The C standard is not the Bible, it is not written by an almighty god. As respectable K&R are, they are humans who wrote a standard for their own needs, based on the state of the art of that time. Sadly C is the work of mortals...
Reading the standard trying to understand the way of god like religious scholars do is a pointless exercise. Modern compiler developers found that exploiting undefined behavior the way we do new leads to interesting optimization, others found it reasonable so now it is the standard.
I think the issue most people have now is that compilers use advanced solvers that are able to infer a lot from undefined behavior and other things, so UB is no longer just "it works or it crashes".
Reading the standard trying to understand the way of god like religious scholars do is a pointless exercise. Modern compiler developers found that exploiting undefined behavior the way we do new leads to interesting optimization, others found it reasonable so now it is the standard.
I think the issue most people have now is that compilers use advanced solvers that are able to infer a lot from undefined behavior and other things, so UB is no longer just "it works or it crashes".