Sure there is, if the attacker has to fulfil some basic obfuscation then it cuts down on the amount of crypto work you have to do before ignoring the packet.
It's not extra security but it is a little extra efficiency.
Wireguard has something like this built in though, the PresharedKey (which is in addition to the public key crypto, and doesn't reduce your security to the level of a shared-key system). It's still more work to verify that than a port knock however.
