Dunno, in combination with having an up to date system following best practices, port knocking is probably going to save you when bots start scanning the internet with the next SSH 0day. Any amount of friction will cause the bots to move to the next IP address.

It's more like "only I know how to find this keyhole". You still need the key then, you're just also adding some defense against picking.

It would be idiotic to use the knock as the only authentication, which is why I don't.

To be quite honest, I just like the aesthetics of it.