This is not even true. This is the second post of this error, On the first post there was a better details, i will "POST" the link here.
Now let me clear something that you missed.
I was tying to set the wireguard with a wifi SSID, and normal internet for the other SSID, Now As you shared the video of surfhark guide about setting the wireguard on openwrt. Yes indeed i followed before when i set the wireguard for my entire router. But now I DO NOT NEED THAT. Because that will not help to fix my issue. Better to say i was tying to set WireGuard just for the guest WIFI.
As my router supports the WireGuard i do not see any good point for using the OpenVPN, as OpenVPN is really slow.