npub1zvjwuxj7n57qgkzlfcalkpq46ks55kuvwq2nu2f5tuxpxntjq6nssdlcud (npub1zvj…lcud) no, the org.gnome stuff is an implementation detail on the GNOME side; the spec is under the org.freedesktop.appearance namespace
https://flatpak.github.io/xdg-desktop-portal/#gdbus-interface-org-freedesktop-portal-Settings