Galeano wrote
and they are all systemd services.
nope, these are "dbus services" , independent of systemd (although sometimes they can reference a systemd service file)
eg. the contents of /usr/share/org.freedesktop.secrets.service
[D-BUS Service]
Name=org.freedesktop.secrets
Exec=/usr/bin/gnome-keyring-daemon --start --foreground --components=secrets
much like the /etc/xdg/autostart/gnome-keyring-secrets.desktop , with a slightly different Exec line
and just for an example of "sometimes they can reference a systemd service file" :
/usr/share/dbus-1/services/org.freedesktop.portal.Tracker.service
[D-BUS Service]
Name=org.freedesktop.portal.Tracker
Exec=/usr/lib/tracker-xdg-portal-3
SystemdService=tracker-xdg-portal-3.service
more likely something to do with dbus ..