Knocking can cut down on grinding. I have in the past created setups where you had to knock prior to establishing a VPN connection, and given the semi-regular problems with VPN implementations I really don't feel bad about that. Fortigate, Sonicwall, Cisco, Ivanti, etc - sure a big part of it is "don't run VPNs based on big legacy codebases" but who's to say there won't be implementation problems found (or introduced given "Jia Tan" style attacks) in Wireguard?
Is knocking incredibly weak security through obscurity? Sure, but part of what it does is cut down on log volume.