They did it with Zelda, no less. BotW had a massive downgrade and Nintendo officially admitted it and even went so far as to "justify" it yet some fans deny it even happened.
You can't really do a fair comparison between different places/camera positions in an open world game because Level of Detail systems will change asset quality on the fly depending on the camera/player position, and considering that that exact area in the trailer doesn't exist in the final game, a like for like comparison cannot be made, unfortunately.