This portal backend is recommended for all GNOME users, even if you
don't have flatpak or snap installed. Host applications can use portals
too.
It's also recommended on RHEL, not just on Fedora.
... to retain consistency with xdg-desktop-portal-gtk.
It's not clear why the Supplements in xdg-desktop-portal-gtk is
specific to Fedora. Meanwhile, at least, it doesn't hurt to keep
things consistent.