This is not normally something that I do, but as a quickie trial I now have five different streams running from my Spotify account. I'm only a few minutes into this experiment and I don't know what will happen over the long term.

There are no intrinsic Sonos rules, a track is a track, however, each service will have different rules about this.

Note that there are two ways to use Spotify. I can't imagine that the Spotify App will allow streaming to multiple players. I'm using the Sonos controller.