There is a difference between jargon in context and the use of those words in a general sense. It can be "undefined behavior" in a general sense, but not necessarily "undefined behavior" in the jargon sense.

After all, if I were to use the words "undefined behavior" in a sentence unrelated to the standards, the definition in the standard of "behavior, upon use of a nonportable or erroneous program construct or of erroneous data, for which this International Standard imposes no requirements." would be nonsense. Same goes in the other direction.