Hmm, good question! This is my Spotify multiroom experience...
So I listen to Spotify Connect on a BeoSound 2, then hit join on my V1, which then joins the BeoSound 2 source..
"{}/{} Spotify - Bedroom, Blessings - Chance the Rapper - Coloring Book" is displayed as a source on the TV display, in the Spotify App the following output is displayed (Beosound 2 + V1). And here is the B&O magic. I can use the BeoRemote one to pause, play and skip tracks...
So as I understand it, multiroom acts as the transport, as long as the source supports Spotify Connect (so not the M3) you can add any multiroom element.
Native Spotify Connect on the V1 would be awesome but this is a pretty good solution.
[Edited to add: Playback is flawless. No dropouts or artefacts ever]