Another thought... it may be related to "resuming" (music) after a call interrupted music that was playing.
Imagine the behaviour where you are listening to music and have an incoming call (e.g. facetime/whatsapp/etc). As the call rings the music is paused (or at least when you answer). When you hangup the call the music generally automatically resumes. So there is some type of play/resume or call over signal that is triggering a play/resume as soon as a web call ends.
The bug in this case is that apple music is trying to play/resume when it was not running/playing in the first place and has no music in the library and has never been used (ever) on any of my devices.
So the question is... are the bluetooth headphones sending some bogus signal or is this related to some "call" API that is being used at an OS level for web calls and how the call ended event is happening.
AFAIK people with airpods don't have this problem, and maybe that is what everyone at apple uses...which is why they haven't noticed/fixed this bug. So is it an OS level thing with (web)call apis or is it something on the bluetooth protocol. If it is on the bluetooth side... then are all the third party manufacturers doing something wrong or do the airpods do something special to avoid this behaviour.
This might be totally off base, but just another idea about what logical area the bug may be in.
Would be logical that most web calls on macOS (zoom, meet, teams, whatsapp, signal, facetime, etc) are using Apple's CallKit APIs (or something similar) to coordinate audio with other apps on the OS (ie pause music when a call comes in).
> coordinate your calling services with other apps and the system.
CXEndCallAction | Apple Developer Documentation
Just guessing as I don't have access to the CallKit or macos source. But I poked around Signal and their webrtc video/audio calling definitely integrates with CallKit. CallKit just lets the os coordinate when a call is happening/ending. Music apps likely use different API that may hook into same events behind scenes...for instance here is an example of how music player resumes after a call or siri interruption:
https://stackoverflow.com/a/63184647/
https://developer.apple.com/documentation/avfaudio/avaudiosession
As Music/iTunes was/is deeply integrated into macos, they may not be using public APIs or event hooks. For instance you can't turn off Music or prevent it from launching (you can only kill it as it launches using helper scripts).... so there has to be some OS-level code (or service you can't disable) that is listening for certain events/states and launching the app.