From which SharePoint columns/fields does
ows_q_USER_Author collect values?
It seems to be a USER (People & Group?) type of column.
Do you have any idea where the
ows_q_USER_Author property is "located"?
I found MicroSoft description related to managed property
AuthorOWSUSER: The name of the user who created the page, but I'm not really sure it works only for pages.