Purpose of role="document"?

I understand why you should use ARIA roles generally, but I don’t understand why Sage 9 uses role="document" on the main content wrapper div in templates/layouts/base.blade.php . My understanding of the document role is that it is implicitly assumed to be the body of an HTML document if it is not set, and so adding it on that div does nothing, and is, possibly, semantically incorrect, if you have anything in the header, sidebar, or footer partials. The only time I’ve really seen role="document" used meaningfully is to distinguish a piece of content as being the “document” part within a container that is marked with with role="application" or some kind of dialog role . There are a few other cases where it might make sense, but not here, that I can see. What am I missing?