A producer getting writing credits is just weird to me...
If you look at the credits of pretty much ANY Hip Hop album, the producer gets a writing credit. This doesn't mean that the Producer wrote the lyrics, they may have helped with the arraignment of the hook, they may have assisted in the formatting and placement of the verses. This is what TRUE producers actually do, they aren't writing the lyrics, but they ARE assisting in the overall formation of the song.
Also, if a track is heavily sampled, the sampled artist sometimes also receives a writing credit. For instance the credits on the song IZZO (H.O.V.A) list not only Kanye West, but Berry Gordy and his legendary writing team who wrote and produced the Jackson 5's original 1969 hit record I Want You Back.