Anything out of scope could not possibly be contradicted. You can only contradict something that you know about. But must be false is saying something we do know is wrong. Let's take a look at a real example from test 71. Pause the recording, try this problem on your own for about a minute and a half, and then on pause when you're ready to talk about it. This is a very atypical phrasing for a must be false type of question.