It is true that it was a Turk that marketed it as such, but it's mostly the Germans that are so insistent on claiming it's a German invention. The only Turks I've seen that weren't largely indifferent were those who made and sold the stuff, but even the non-döner-worker Germans can be weirdly militant about it especially after a few drinks.

In any case, why it was named that is irrelevant to the point. Which is that we're being pedantic in this thread and, strictly speaking, the name is wrong. It is in gross violation of the unwritten döner naming conventions. But obviously I'm not holding my breath for any official rebranding.