Is this an issue of documentation or design? Sure, we can say things like that if that’s how we decide to write the function (and if we end up retaining any non-obvious choices with respect to strictness, we certainly should document them), but figuring out how the function should behave should come first.
I would imagine that not every part of base has been specified out to the detail of strictness signatures. I’m not sure if it’s worthwhile to do so, either, but for some high perf assurance functions it might be.
Unless there is a compelling user story, I’m doubtful that Product deserves such attention, but it’s up to the CLC to decide.