If you have a specification for a program saying "input: variables x and y, output: z holds x+y", you would probably be annoyed if someone coded "x=0; y=0; z=0", though.
Just playing devil's advocate, I think the headline is not bad (could be less ambiguous, but sacrificing brevity)
This "illogical" double negative shows how English is not at all like algebra. English is not a set of formal rules - there is no formal authority on the language. The rules that exist are derived from how English is commonly used - descriptive rather than prescriptive. This is why dictionaries are constantly adding new (sometimes annoying) words, and the Chicago Manual of Style is on its 18th version. For example, I was taught that "they" could never describe a singular person, and one should assume "he", "she" or "the suspect". Not so anymore [1]. The language, its constructs, and implicit rules are always changing, regardless (and irregardless[2]) of how you criticize those that speak it.
Just playing devil's advocate, I think the headline is not bad (could be less ambiguous, but sacrificing brevity)