One user over at NeoGAF claims a copy of Assassin's Creed II on Xbox 360 came with said insert, while further evidence from HipHopGamer shows what appears to be the alleged insert (it's since been removed from the original video; but Kouppa-Network Live still has it up). Logic points to the demo being the same portion of gameplay we checked out back at E3, though there's no evidence to verify that.
We've contacted Ubisoft for comment and will update this post when we hear back.
Source - NeoGAF post
Source - HHG video with insert reveal removed
Source - Pulled video showing insert