Every FS map since beginning has been and is open world. You are free to move around openly in the map world, as opposed to being guided through a pre-defined route, like in Super Mario (to use a simple example). Nothing new or exciting in that particular part of the press release.
Much more interesting is the graphics overhaul, the dog, the new maps, and "brand new mechanics", whatever that may be (hopefully physics mechanics, like deformable terrain ).