It was suggested client developers that it would be helpful for a ping-req message to work the same in connected mode as in sleep mode (i.e. receive outstanding messages). The justification was that it would help them to know if they are able to go to sleep.
My feeling is, if we solve for the ping-resp containing queue state and this is returned regardless of CONNECTION status (ie. SLEEPING or CONNECTED) then we can leave the CONNECTED variant to simply respond with the ping-rest state WITHOUT marshalling the queue.