Because all the mouthflaps are terribly wrong.
Anniversary is amazing, but it’s horrible to watch the cutscenes now. The opening scene looks like Keyes has cleft lip. In the scene where Johnson is talking to the Marines, they say “Sir yes sir!” but their mouths continue to open and close after. Most of the time when a character talks, the mouth flaps don’t even match what they’re saying.
This is a huge problem for the game.
Other than that this game is awesome. No flaws (except for Johnson looking nothing like he did in Halo 3, which is his most up to date appearance, and Cortana is blue for some reason.)
Also thanks for making Cortana’s -Yoink!- HUGE.
Mouth movements are the same as those in Halo CE. That’s why they look odd with the new visuals.
As to why they couldn’t just replace them? I’m not sure.
I think there’s new movements in the mouth. In the original the mouths just opened and closed. Also the cutscenes have been remade.
The answer to your question is yes. Yes, Halo is a Japanese movie.
It looks like the mouth movements are a bit behind the audio.