OneNote: separate Quick Notes section or part of default notebook?

I have had my Quick Notes section as part of my default notebook (username@tenant, located in ODFB). An update or three ago, that changed to a free-standing Quick Notes.one section, located in my default location for new OneNote files. I changed it back. Everything works fine.  But Microsoft must have had a reason for that switch. What are the functional differences, including database integrity, between a Quick Notes section that is part of a notebook and a Quick Notes section that is standalone?