I don’t understand how one could possibly think that requiring a Google account would make it easier to onboard new users…
Simple. "Log in with Google" is a lot less friction than getting people to sign up to a new service. Even more so for a mobile-focused application like Surf/Flipboard.
doesn’t exist elsewhere.
Isn't it "just" a feed reader with a pre-curated list of feeds? Doing that is not complicated. The hard part is doing it in a way that it is easy for non-techies.
You are right. I thought it was just a different take on the flipboard client, but more focused on the different feeds.