In a nutshell: bloke's daughter buys DLC, but acidentally buys the PS3 version instead of the PS4 one on Sony's awful web store. Asks Sony if they can swap it the right one - 'Computer says no!'
Now I know that this is customer error, but any right thinking company would just revoke the license to the PS3 DLC and give them the PS4 license instead (given that they're the same price). A tiny gesture of goodwill that would cost them nothing and help prevent driving customers into the hands of competitors. But this is Sony.