The song "Oh Death" by Jen Titus was produced and written especially for the show Supernatural.

I think they meant in the sense that Jen Titus sang that song only for SPN, not that she originally wrote the song.
I will accept that perhaps that blurb was written by a fan who did not understand the difference between writing and aranging a song.

Because it is a badass arrangement. I want some AMVs.