"assume unbelievable X".

Only this is not an unbelievable X, its an entirely believable X (I wouldn't have any reason to ask an >unbelieveable - as would anyone asking a question - unless they are actually trying to trick you with a >question). In fact - assuming that people are asking you to believe an "unbelievable X" is a strawman of the >argument in point.

Are you sure that's how you want to defend your question? If you defend the question by saying that the premise is believable, you are implicitly endorsing the standard that questions should only be answered if they are reasonable. However, accepting this standard runs the risk that your conversational partner will judge your question to be unreasonable even if it isn't and fail to answer your question, in exactly the way you're complaining about. A better standard for the purpose of getting people to answer the questions you ask literally is that people should answer the questions that you ask literally even if they rely on fantastic premises.

Can you do me a favour and try to steelman the question I asked? And see what the results are, and what answer you might give to it?

A similar concern is applicable here: Recall that steelmanning means, when encountering a argument that seems easily flawed, not to respond to that argument but to strengthen it ways the seem reasonable to you and answer that instead. The sounds like the exact opposite of what you want people to do to your questions.