Hmm, looks pretty fine off hand although I think Zone In would typically be set to WAN and Zone Out would be LAN in this scenario. Also I think only UDP is needed for Wireguard as I recall.
We can double check that the rule is definitely being set on the router by opening up a terminal (shift+click on the router name in the teminal) and run the command uci show firewall. That should spit out all the firewall rules that have been set on the router.