I believe what happens is that if you cook rotten meat, the (rotten) flag transfers over. Except that it’s not an item flag; it’s based off the birthday of the item and its spoilage time. So when you cook rotten meat, you get cooked meat (rotten).
Except that beef jerky doesn’t spoil, so it can’t get the rotten flag applied to it.
And besides, trying to prepare rotten meat in such a way as to make it appear not rotten - isn’t that what curry powder was originally for? (Maybe that’s an idea for a new food item)