Only sane explaination would be that there's excess capacity holding of 2As with NR, so they're hoarding some 2As with short rake of AP.
3A sees excess demand/occupancy few days a month in this route. But I think 2A has never reached WL.
It likely never will, considering the below avg. timings & running time, people won't prefer 2A (Fares rival Flight from VSKP!!)