Yes, you are correct... not new. Sorry.
Yes, where does one put this "new box" information, in the quiz settings or in the edit quiz page?
Let's see. When a student click on a link to a quiz, they get the "Description" information, from the quiz settings. This added box is a box that shows only after the student clicks on Attempt, and it only shows right before the student finishes. So it seems to be contained within the quiz itself, and not part of the definition of the quiz. So this would imply that this feature become part of the Edit quiz step.
However, I could argue the opposite. Let's say that I am setting up a "template" for quizzes, prior to adding questions. If I wanted to use the same wording for every quiz, I would want this "Summary Statement" become another item in the "quiz settings."
Hmmm, I guess that I could go either way.
In your example (which is just an example) it seems that I would build this into the Description for the quiz. As I think about how I would use this feature, I might want to remind students "Remember that you must upload your work file after you submit this quiz." This kind of statement would logically occur right before the student submits, which suggests that the feature becomes part of the "Edit quiz" step.
Let's see where I end up.
Anything that I want the student sees before Attempting the quiz goes into the Description field, in the Quiz settings. Anything that I want the student to see right before Submitting goes into the new Edit Quiz feature. This seems to provide the most flexibility and some of the overall logic. I can live with this.