I don't see a violation of the standard in this case. But I think that this here is a matter of interpretation. Some people interpret the standard in a shallow (literal only) way, others think a bit more about it and take into account related definitions, context and facts. To me "undefined" does not necessarily mean that the behaviour is undefined under all conditions.
If you look back I wrote that "I prefer", so it's a matter of taste and experience what other people do and suggest.