Think of the SONOS Apps as simple remote controls, they don’t store or play any music. As you have discovered, once the controllers start music playing, the controllers can be shut down because the players interact with the music directly. Some Apps, such as Spotify can play music through a SONOS system. in this case, shutting down the App will stop its music. Likewise, if a phone/tablet is streaming via AirPlay 2, shutting down that device will stop the music.
In my opinion this is a great feature. I’m a speed freak and I don’t like my computer being distracted by delivering music to a speaker. If the computer crashes or I need to take it down for an update, the music continues to play.
