First, who cares?  As long as the income flows through to someone, and there's no obvious attempt to divert it to lower-bracket beneficiaries, IRS doesn't.  Not that they audit any 1041's, anyway. 

Second, if the deceased was entitled to 100% of the income for half the year, how close can you come by giving her 50% of the income for the final year, and the other 50% divided among the surviving beneficiaries?  Maybe if more of the income was received late in the year, as with capital gain distributions on many mutual funds, you have to put your thumb on the scale and make it more of a 40%/60% split.