It's ordered with networkd, but just in case. Lintian complains:
W: systemd: systemd-service-file-shutdown-problems [usr/lib/systemd/system/systemd-networkd-persistent-storage.service]
Follow-up for 91676b6458
Then, this introduces systemd-networkd-persistent-storage.service.
systemd-networkd.service is an early starting service. So, at the time
it is started, the persistent storage for the service may not be ready,
and we cannot use StateDirectory=systemd/network in
systemd-networkd.service.
The newly added systemd-networkd-persistent-storage.service creates the
state directory for networkd, and notify systemd-networkd that the
directory is usable.