Uh, so, systemd don't recommend to use `sudo systemctl start blah`. Their idea is to use `systemctl start blah` and have polkit handle the authentication. Not sure what's unclear here.
The difference is that with `sudo systemctl ...` systemctl is run as root, but with PolicyKit only parts are. And if I understand it correctly PolicyKit allows more fine grained control over permissions than sudo.
"Did you know that polkit, the systemd replacement of sudo,"
He calls it a replacement of sudo which is is definitely not.