Your definition's right in the sense of what "not supported" allows the user to do. But the term also means "if you try this and it doesn't work, we're not resp

Your definition's right in the sense of what "not supported" allows the user to do. But the term also means "if you try this and it doesn't work, we're not responsible," and that's the key thing. Some companies (and programs, and programming languages, and so on) make it easy to do unsupported things. Some make it hard. None will accept liability for it. Hardware manufacturers are on the hook for so many potential problems, defects, misconfigurations and misuses that it makes sense from their perspective to support actively only those things they can guarantee will always work. Not things which the hardware can theoretically do but which might not always be the best idea, things that aren't possible now but might be in ten years, etc.