Hi I sold my device which I used for Spotify Connect.  I removed the device from de device list. 

But the device appeared again in the list. I could even connect and play music and control the volume. I verified this with the new owner of the device.

So according to me, spotify should not start streaming to a device, when this device is not accessible via your own network (wifi, airplay etc etc) !!! 

Which usage scenario needs this "feature"? I can't think of one...

A scenario which won't make you happy: You had a party, a few people connected to your device to play music. They go home. They can still play music on your device. Even when they are not  connected with your wifi network...