Unfortunately it's what happens when mass producers/processors of food get their hands on something that is so processed you can't easily and readily identify its contents. No worst than what are called wieners/frankfurters/hot dogs in the U.S. though those don't really claim/allude to be anything (other than "meat").

As for the health of doner kebabs, I saw a travel show that went to where the stuff (not just the town but reputedly, the restaurant too) originated in Turkey. The restaurant served you the kebabs on a plate and then pouring melted butter on them!