User blog comment:D. Cello/AC: Revelations Gameplay Trailer/@comment-25419730-20110820052351/@comment-1866320-20110820155207

Yeah I noticed that too. I like to think that since the memory obviously took place some time before AC1, his different face and voice is acceptable. They may change it when Ezio starts to relive some of Altair's newer memories (somewhere in or after AC1).