Earlier quoted context omitted.
What do you see as being the ideal UX for switching between devices?
Not OP, but... Start by listening to something on my iPhone. Sit down and turn off music on my iPhone. Open up my laptop. It unlocks with my Apple Watch. I pop open iTunes or Spotify, hit play with my Air Pods still in. This could also work with my iPad as well. I open my iPad, stop playing stuff on my iPhone, and start playing something on my iPad. I shouldn't have to swap. Apple knows it's me and knows which device…
I could be using the MBP and want to hear music from the iPhone though.