With Orca 3.12, when I choose, in Writer, Tools -> Preferences -> General, the checkbox "Use LibreOffice Open/Save as dialogs", these dialogs have a problem.
Indeed, in File type combo boxes, when I scroll down or up with arrow keys, Orca cannot speak the items. To get them, I need to do tab (go out of combo box), then shift-tab (to come back). Here's the orca behavior:
*** This bug has been marked as a duplicate of bug 82998 ***