Format and design correspond to the division of rhetoric called delivery. On paper, delivery is concerned with the appearance of the document and how it visually makes contact with the reader. Even in academic writing, students have some opportunities to make choices of fonts, graphics, and white space. Sometimes the writing task will tell the writer how to proceed. Other times, a writer may have to try different strategies.
Writers always have to follow the principle, Do what works.
Take me through your process. By learning how writers went about writing, they can suggest alternate strategies. They can diagnose poor writing habits and suggest new ones. They know the writing of their disciplines and the writing processes that work best. Their students do not yet know these things about particular disciplines and need to learn them.