I don't have a Sonos but interested in this because I have Chromecast Audio. Similar concept- audio not being played on phone or even streamed from phone, but phone acts as a remote for speaker which is doing its own streaming and playback.
I'm interested cos I never thought we'd see this supported in CC because no audio is actually playing on the phone. I'm guessing it just got approval to stream silent audio or something, which lets it hook into CC, but its commands are forwarded to the speaker like the in-app controls
Anyway, question about the mechanics of it. Firstly, when you play something else (say with another music app or whatever), I'm assuming CC switches to that new app, but the Sonos device keeps playing the music it was playing? Secondly, when you return to the Sonos app, does it return to the CC? Thirdly, if the other app you were using supports background audio, has it now been paused by returning to the Sonos app?