Could be but the berth allotment is also same when u closely look into the berth numbers mentioned in the CABIN's and COUPE's.
I myself saw my COUPE named C and berth number 9 and 10 marked inside the coach.
Hence 13,14,15,16 could be a CABIN also, though the official site say there has been no upgradation in this train today.
We never know...
more... the convention followed because there has been no fixed convention to earmark extra coaches attached.Station do according to their wish.