Very interesting. That's clearly the list of rooms from the public room list, but it looks like we are responding to a commands request with a list of rooms :(
This'll be because XEP-0050 uses the whole disco#items stuff to get a list of adhoc commands. The fix would be to check the node attribute of the <query> element, and not send any items if it's an adhoc command query instead of just a room list query.
I joined #fdroid#matrix.org@bridge.xmpp.matrix.org using Gajim, opened the adhoc commands menu ("Execute command") for the channel, and got this -
XML console output when performing this operation - https://gist.github.com/contrapunctus-1/f8ab36b1897a6a25b766bee18ff6c629