Sorry - I didn't notice that this has already been reported...
This probably isn't the right place to submit a bug report for connman, but I'm not sure where is the right place.
In the file /storage/.config/wireguard/wireguard.conf,
I set WireGuard.AllowedIPs = 10.0.0.0/8 (rather than the suggested 0.0.0.0/0, which routes everything thru wireguard.)
Unfortunately, routing table still routes everything thru wireguard, not just 10.0.0.0/8.
Thanks.