Maybe IR's push for their newish 3E rakes over the conventional 3A ones. I see no practical purpose though I personally would have not tinkered with the config since 3A is slightly more comfortable[due to more width of seats] when compared to 3E. But it's happening in many trains. Check out the Krishak Express. Also originates from LJN, got all it's 3A coaches replaced by 3E.