WireGuard is designed to be silent preceding a cryptographically authenticated INIT message. It's a superset of whatever security features you'd get from "knocking".
“Port knocking” et al were most definitively not.
OpenVPN is basically 1000 configuration options and magic incantations wearing a trenchcoat, and if you get any of them wrong the whole thing crumbles (or worse, appears to work but is not secure).