@John no, unfortunately

@user3439894 Yes I am aware it's not implemented for macOS; that's why I included that section of the man page.

Yep, this was my issue. From an application, I was passing a string into a utility function located in another file, which did open POSIX file theString. I refactored my code so that the app would pass in the file directly and the utility function would simply open that file (theFunction(POSIX file theString) and open theFile).

I had 3 copies of each contact after linking contacts from my iCloud and Exchange accounts, and this fixed it for me. Thanks!