It is the default behavior. If you setup WireGuard Client on GL routerA, and setup WireGuard Server on GL routerB, when the WireGuard connection between routerA and routerB is established, you can access LAN clients behind your VPN server from VPN client side.
But if you also want to access LAN clients behind your VPN client from VPN server side, you have to modify as I mentioned above, if you don’t need this, you don’t need edit anything.