I know Bethesda mainly uses the Gamebryo engine, created by someone else and just kind of plugs pieces and parts in , which doesn't take as much effort as creating an entire gaming system from scratch. All the devs are doing, in my opinion, are programming a few aspects here and there, but mainly modding something someone else already created and calling it "fallout 3" Thats why the architecture, etc wont have any kind of fallout look to it in my opinion, only signs, billboards, doodads, etc that the developers actually put in themselves MAY have that look.