No, question banks cannot be scanned for file usage due to limitations with the Canvas API. Since TidyUP does not scan the quiz questions, they will not appear in the Used In column of TidyUP. In addition, files that are only used inside a quiz question are marked as Unused in TidyUP.
Please manually verify files are not being used in a question bank before deleting them. The fastest way to do this is to go to the Canvas course menu>>Quizzes>>Manage Question banks (in the overflow menu)>>question bank. You will see previews of all the questions in the bank. The question's directions are included in these previews, so you should be able to tell if an image or other file is being used in a question. To view the answer choices, check the box that says, "Show Question Details".
If you have images or other files that will be used in quiz questions, it is recommended to place these files in a specific folder to indicate that they are being used in a question. By organizing the files in this way, it will be easy to manually verify which files are or are not being used in a question bank before deleting them in TidyUP.