Google needs an entirely separate brand/entity to launch these things. Nobody wants to hang out at the utility company office no matter how much free coffee they put in the lobby.
From the very first paragraph: "Google’s Area 120 team, an internal incubator that creates experimental apps and services, has launched Keen..."
In a way this is exactly what you're suggesting: an entirely separate identity [1] to launch these experiments, and avoid direct association with Google's core products. Keen's site[2] only mention Google in the footer.
Of course, "Google launches a Pinterest-rival" makes it sound more juicy than "Area 120 launches an experimental product"...
(disclaimer: Googler, but no affiliation with A120 or the product. I'm hearing for the first time here)