What's the term for contradictory sentences or phrases?

"Don't include too much technical detail if it doesn't add value. "

In the sentence above, you could remove the last clause "if it doesn't add value", and the remaining statement "Don't include too much technical detail" would still be true. Maybe put another way is that this sentence makes it sound like it would be ok to add "too much" technical detail "if it added value". But then is it really too much?

Does anyone know of a term for this concept? I'm trying to write a rule for it in a company style guide, but I'm struggling to find a term for it. I thought of labeling it as "avoid contradictory/paradoxical statements", but it seems like there should be a better way to describe this?

Doubling negatives is frowned upon in guidelines for Plain Engish: "Use extra technical detail only if it adds value." https://www.plainlanguage.gov/guidelines/concise/use-positive-language/