Google actually has an internal social network and the main purpose is basically to make fun of google's messaging apps.
It's not just for that. They also post screenshots of other social networks referencing its meta-memes.
So now they have half a dozen messaging apps. Why does Google love building messaging apps? They probably could use better person to person communication instead to consolidate them. Messenger, Hangouts, Alto, duo, etc
It was a joke. The app in question is a demonstration of their secure web push protocol layer. It's not a product.