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.
Well, since this was the recommendation from one of the polkit contributors... I'm not exactly sure what you mean. Perhaps you can enlighten me with your wisdom.
Calling it the sudo for UIs seems reasonable. It lets you manage the permission level of the UI you're using.
Does it do something else?