It is a matter of communication wether you want to use the unit sections, or stack the different modules into the same section.
When should you use Unit Sections, and when should you not?
If you want to create a clear and visible progression for the student, using sections would be a great tool. The student will then move from section to section, and only see the modules and assignments you deem the most valuable on every page. If an item contains a lot of modules, we recommend that you divide your content into sections.
If you only have a few Modules per Item, Sections are not necessary.
If you only have one video with a few attached questions in an Item, the best solution would be not to use Sections. But say taht you have to videos, each with questions or text attached, we would recommend dividing the content into two separate sections.
This is what the sections look like in the Course Builder: