Minecart with TNT fails to return correct items when removed by player

Players places a 'Minecart with TNT' item onto a track, spawning a TNT Minecart. Removing the cart by punching it - with the aim of returning it to an item - instead returns a standard, empty 'Minecart' item and no TNT. Occurs in both Creative and SSP gamemodes. In SSP, this would result in the 'vaporizing' of invested TNT. When item is collected in inventory, it is a Minecart item, meaning this is not an issue with appearance / incorrect texture display.