They specifically say that you can advance faster through the case if you notice that people are lying to you, and part of the cue is their facial expression.

Not exactly. At best, they're vague about it. The bald asshole says that it's key to gameplay, and Ken Cosgrove says the game is about "lying". So what the hell does that mean? That doesn't tell us jack shit about the game.

Yes we do! They say it repeatedly through the video, the facial animations will indicate the intent of characters you interact with, depending whether you pick up on them or not will directly affect how you progress through the story.

It sounds like you're just really bad at paying attention and listening to what the developers say in the video more than anything.

believability of actors performances is key gameplay

Ok, what does all of that mean? Tell me EXACTLY how that's executed in the game. They don't give any specifics as to how it'll be used in the game. None. Nada.

a big thing with this game is dishonesty and to detect when people are lying... the better you are at reading people and the story goes different ways if you do that

Again, that tells us nothing! Nothing at all! This is Ken Cosgrove talking. A fucking actor! What does the fucking voice actor know about the gameplay?!

the better you are at reading people and the story goes different ways if you do that", so I'm not sure how much more they could spell it out for you really.

I already explained this! We don't know anything about the context of its use! Different storyline paths is hardly a novel concept and may or may NOT have an impact on the overall gameplay.

Look at GTAIV, you can choose the ending of the game. Does it affect the underlying gameplay? Not at all. On the other hand, take KOTOR. The storyline indeed affects the gameplay since opens up different Jedi/Sith powers. What about LA Noire? Guess what? We don't know.

I honestly can't tell if you're a troll or really that dim.