on small displays the playback-tab cant show all infos. Especially The multiroom-device bar has to been scrolled up to see which device is currently shown on display because there is no other identify info about the active shown device.
If changing the multiroom-device the background-image of the selected device (of its own) should be changed too. So there can see simple which device is actively displayed to operate - or put a simple info of the currently shown active device e.g. left from the congiration-icon in the top bar.