Amazon Echo - TTS to Echo Stereo possible?

I’m using the amazon echo binding from the first days on and it works perfectly since then. Now i changed one of our Echoes to two echo stereo and a sub as a so called “Home Cinema Group”.

I can’t see the new stereos as a single echo in my amazon echo binding and also there seems not to be a tts option to the group “Home cinema”.

Is this not supported or do i have to do anything to get this running? We rely on TTS output at several triggers for a long time and want to use this again with the new echo stereos.

Best regards