Seems that I can’t comment on my original thread:
I recently was annoyed that I was casting through the web browser and paused my music to join a work meeting. About 15 minutes later my music starts up in the middle of my meeting! My workaround at the moment is to completely close the web browser tab so it doesn’t try to start up my music once the chromecast connection disconnects.
One suggestion: Plex implements this by asking “Continue playback here?” That might be a good way to implement, so that my music doesn’t automatically start playing without my input. This pops up when chromecast disconnects, whether manually by me or automatically after the time period (I believe 15 minutes).