... Seriously, what kind of bullshit are they selling? Lets make this crystal clear:
Playing many diffrent games, that have diffrent gamestyle, reactions to human input (diffrent speed of rotation with mice for example), and compleatly diffrent storyline improve brain activity.
1 Reason: everytime you are learning something new.
Its quite obvious to most people that if you play always the same raceing game, you are not gonna use your brain much. In fact many peoople tend to say that when they do, they feel like they do it automaticly, and feel sleepy (the brain uses that time to partially rest, as it can do that job and rest same time).
Now, anyone can probably guess that this is not only logical, but also a fact known to humanity.
My 2 cents
.