OpenVPN does routing a tad differently, but same point applies. Network clients need to know where to go to find a route that isn’t part of the home subnet they are joined too. With containers in the mix without bridging, the host needs to know that the WG subnet can be found at the router.
That may look fine from your router’s perspective, but if your network clients don’t get an updated routing tables, they won’t know or possibly accept traffic from the new subnet on the VPN.