Often been annoyed when despite nothing playing on one device, it wouldn't switch. Great tip, thanks!
I understand this as being able to cycle through all combinations of two stored devices. I'm only able to select the next previously paired device, not a combination of two devices. Have I misunderstood the GP? I can't find any mention in the help about selection of two devices, only iteration of previously paired devices.
When a new device is selected, the least recently selected device is disconnected. So once your first device is selected, start cycling again and select your second device. It's just a FIFO (First in first out) queue of devices.