I seem to run into many stories on SOL that contain the phrase "needless to say ..."
It makes me wonder, if it IS needless to say, why does the author say it anyway?
If it's NOT needless to say, then saying it is is a contradiction.
It's generally a back door approach to explain what ALL the characters in the story understand, but readers (especially non-native English speakers) may not.
Thus, it's not really a contradiction, but a simple annoyance for those who already know the explanation long before it's stated for the few who might not know it.
For example, in a Columbian drug drama, you might use:
Needless to say, one doesn't cross El Chappo.
as a reminder that you don't piss off the bear who's likely to rip your face off. It's not the reminder that's never spoken of, it's the actual criticism that's never spoken.
For any more meaningful interpretations, we'd need some examples from the books in question, as they might have had a different intent entirely.