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)

[1] https://area120.google.com/

[2] https://staykeen.com/home