My phone screen is broken, so I use Siri a lot lately. I was listening to a song on Spotify, and asked Siri to "Send this song to Alice". Everything seemed to go fine until later, I saw the link was Apple Music, not Spotify.
Alice likely never listened to it because we only ever share Spotify links.
Also what is happening behind the scenes to give Apple the song from Spotify? Are they just accessing current song on Spotify? What if they don't have it on Apple Music? Or are they running pattern recognition on the audio output to determine song?