I think for a homework question, "This is a homework question, and I'm totally stuck" would be a perfectly good way to preface a question that would almost always get someone a useful answer here.
I don't think the preface "This is a job interview question, and I'm totally stuck" would get treated the same way without a much more detailed explanation. So, I think it's worth distinguishing the two, and responding differently.
And, in general, while not answering is an option, and sometimes an effective one, very few questions go unanswered here. I have seen a lot of these questions treated as if they were homework questions (a bit of snark, a pointer to the documentation, almost always ultimately followed by a fairly comprehensive right answer), and I think there are reasons that could be harmful when it's actually an interview question.