Most projects under the "google" org will have exactly the same disclaimer about not being official Google products.
But at least they are under the Google organization. Thing is anyone could create an organization, name it something like "googlesomething", use Google logos, and design it in a way that some users might believe it has an official connection.
Crazy.
And this project uses "google" in its org, so I would assume it is offical or at least lawyers are running toward the owner with lawsuits.