Why do we see this message, Failed to talk to shutdownd, proceeding with immediate shutdown: Connection refused?

Issue

After creating the following scope unit, any commands that need to talk to dbus for IPC communication of systemd mechanisms fail.

# systemd-run --unit=topU --scope --slice=topS top -b
# systemctl status topU.scope 
# systemctl daemon-reload

# shutdown
Failed to talk to shutdownd, proceeding with immediate shutdown: Connection refused
Failed to open /dev/initctl: No such device or address
Failed to talk to init daemon.
# systemctl status dbus
Failed to get D-Bus connection: Failed to connect to socket /run/systemd/private: Connection refused