Is the Halo 3 "Believe" commercial actually a playable level?

[Ammon Salmo]

In the commercial, Chief is captured by a brute as is about to blow himself up with a plasma grenade. I just finished the game on "normal" difficulty and no such scene exists. That kind of thing doesn't sound like something Bungie would just throw in a commercial as advertising. Mabey its in legendary difficulty?

 

[Lee R]]

I know the end scene for is different on legendary.
I completed it, but i let someone do the last level with me and he skipped the clip