This question — "Do PC screens in Australia scan from bottom to top?" -- explain the humour please — raises what I think is an interesting meta point. I've seen a few questions like this where someone asks what he thinks is a question about the English language, but in fact the correct answer is that it's not really about language but about geography or history or whatever. People often vote to close such questions as "not about the English language".
I think this is incorrect. Yes, if someone asked a question that was clearly and obviously about geography — What is the largest river in France? or some such — that should be closed as irrelevant. But in cases like this, the OP thought, in my opinion quite reasonably, that this was an idiom or some other quirk of the language that he didn't understand.
If we say that questions that sound like they might be about English but ultimately really aren't are disallowed, then we are, in effect, requiring the OP to know the answer to his question before he asks it.
It's often said on here that we're trying to build a repository of questions and answers that are available for reference. Is it possible that others in the future might have a similar confusion about whether something is an idiom or a geographical reference? Surely so. If such questions are disallowed, then we're ruling out useful answers.