No actually you may find in some trains(which were rebuilt during Our Former Rly Minister Lalu Prasad's Era after the implementation of the Side Middle Berth),that the 3 passengers will be in the Side Seats only in the Night Time.As per ur example give,if its a 3A coach then one of the RAC passengers(of berth 15) will be sitting in the designated berth 15 & the other RAC person may occuppy a seat in close vicinity to his berths either in 9,10,11,12,13,14 without disturbing the Confirmed passenger in the Seat 16.