Well I had severe doubts about that Unrecord trailer. Still do to an extent. It's a weird trailer, I'm not sure why faces are censored my instinct was that it was just to hide that it was real footage as a perfect face would be a dead giveaway. But the dude falling over at the end looked very fake video gamey...
On one of the steam screenshots I can see grass clipping through a bookcase so that certainly seems like in-engine.
I'm sure that trailer is BS to some degree and the final product won't look that good but it might not be a complete fabrication.