To get rid of this commercial ban / mistreatment of clients I made some thoughts and developed a very simple and cheap solution.
To play the same music synchronized in all of my rooms (setting with a S2 net and a S1 net) I started a spotify session. In this spotify session I plazed another user which is also under my control. After I done so I activated a user on each, S2 and S1.
As soon as I‘m playing Music in one of these Spotify Users the music plays synchronized in both S2 as well as S1 net.