After reading an existing/closed thread (BGP prefixes accepted, but not installed into routing table), I am having the same issue, but a reboot is not solving it!
I have a WG0 VPN up and running, with eBGP running across it (quagga/bgpd) and they are all seeing the routes in the BGP table at both ends, as expected - however, the routes will not get installed into the routing table for the clients to use on my OpenWRT box.
I have built the same on a non OpenWRT box and appears to work fine - although I am having to insert a parameter which is related, but I don't think would solve this issue. It appears that the "table = off" is not used in WG version on openwrt.
Address = 10.0.0.4/24
ListenPort = 41194
PrivateKey = yD1kvcXeocmUdJp44jsdf32fd33vFVjFOryty3BlU=
Table = off