Can't add wireguard interface to relay bridge - LuCI bug?

I have a router in a relayd client bridge configuration, and I also run wireguard to allow remoting in.

It works well except for the fact that remote Wireguard clients can't talk to devices physically plugged into the router. In order to allow that, I had to add the wireguard interface to the relay bridge. It works great, but I've noticed this can't be done with LuCI. I had to edit /etc/config/network manually:

config interface 'repeater_bridge'
        option proto 'relay'
        option ipaddr '192.168.x.y'
        list network 'lan'
        list network 'wlan'
        list network 'vpn'

Before I go and find out where the bug is and patch it, I thought I'd ask if this is for some reason intended behaviour. Is there some reason the LuCI relay interface excludes wireguard networks from its list?