Whenever mobs are burned, in this instance pigs, in creative mode they won't drop the cooked version of their meat. I use various contraptions such as dispensers with flint and steel, lava on the animals head, or manually flint and steeling them and they won't drop cooked meat. However, when I go to survival mode, they'll always drop cooked meat.

Additional Information: Done on Peaceful Mode
Done on Superflat World created in 1.5.2

Edit: Happened when I tried it in 1.5.2 and the 1.6.1 pre-release, however I re-entered the world in 1.5.2 and now they seems to always drop cooked meat like they should, before they would only drop raw porkchops.