if its not in engine how exactly is that proof of anything? The only thing it proves is that they can hire a third party to do a CGI cartoon. as a means of hyping your game there's nothing to show from a CGI clip that proves or disproves the concepts or quality of your game. CGI is a waste of time and resources especially when you consider the crowd that CD Projekt makes games for and what visuals that todays game engines can achieve.
Much like KZ2 did when they showed off that CG demo during E3. It'll give an idea of the atmosphere, locales, music and characters that'll populate the world.
Pertaining to hype, it was generated by the people who ran wild their imagination and interpretations. If the teaser is to be CG then I am pretty certain that soon (perhaps E3) we'll see something in-engine.