When adding this section, use id="dialog_nonmodal" on the section element; this is the ID of the stub that was in early working drafts.

When working on this issue, there is some old content that may be useful in the file aria-practices-DeletedSectionsArchive.html.
The relevant section can be seen here:
https://rawgit.com/w3c/aria-practices/master/aria-practices-DeletedSectionsArchive.html#dialog_nonmodal