Graphically, and artistically it was impressive, but it unfortunately contradicts everything Letho says when you meet him for the last time.
In that dialogue he mentions that Demavand was killed in his castle and that they used Sile to detect the guards, that all three assassins were involved, that they maneuvered through tunnels, and that they barely got out alive.
In contrast, the new video shows Letho sailing up to the King's boat and handily killing everyone. No Sile, no other assassins, no tunnels, no near death escape.
While I applaud the developer's artistry, this kind of ruined the ending for me.
indeed, i wondered about that. however, letho wasn't extremely specific, and the only thing that sticks out to me from what he said is they had to "navigate a labyrinth", which may have been metaphorical. after all, he's not as dumb as he looks. did he actually say he killed him in the castle, and that S&A were there? and i figured his awesome freeze bomb was a result of sile's magic.
also, the outro they added is also great, gives me a strong desire for witcher 3