TLDR: Once you connect Spotify to your Sonos on the local network, the Spotify app can control it remotely over the internet for ever and ever more.
****NB: I do not believe this to be related to adding Spotify as a music service. The feature described above works on a Sonos without Spotify added as a service.
How do you boot a remote user off of the Sonos?
Appreciate a real answer from someone who has done this or a support rep, there is a lot of erroneous or out of date info on the internet. My guess is factory reset might work, but I’m not sure.