https://bugzilla.redhat.com/show_bug.cgi?id=1534446
--- Comment #10 from Robert-André Mauchin zebob.m@gmail.com ---
_is this implemented anywhere yet, or there are still some places where it is expected to be in /usr/share/appdata.
I don't know to be honest.
The guidelines always reflect what should be done for Rawhide, not previous release.
You could move the file in install to but it in the right location. You could also notify upstream that %{_datadir}/appdata is a legacy location as explained by https://freedesktop.org/software/appstream/docs/chap-Metadata.html