This isn't coming out of Google, it's coming out of Codemasters. And it's actual video of the Stadia version. So what exactly could be discredited? It'd be a little bit softer image due to the video compression as opposed to direct feed is all.
First, sorry... Not trying to rain on anyone's parade. That was lame of me.
General marketing buzz has set expectations a certain way. I'd be hesitant, with the hands on reviews that have come out thus far, to trust the graphical fidelity of any official advertisement. Every game that we've seen hands-on reviews for has been a poor imitation of what was shown in official trailers, etc..
This conversation is also making me ask, why does Bungie, for example, keep quiet about the graphical fidelity of the Stadia port when it clearly didn't meet expectations. I am sure there's some sort of contractual nonsense here, but still. It's not a good look for Google or anyone they're collaborating with.