I didn't have the same experience, although I am using a couple AdBlockers. You might have a cookie already on your browser to trigger that login modal. There's also a possibility a major publisher like the NYT is trying to close that Google loophole.
Thanks for the tip! You were right about the cookie. Clearing browser history got me 10 free articles, additional googled links showed the dialog again.
Have you ever heard of Quora?
This is worse than Quora. I'm able to open a googled Quora link just fine and read the whole thing. It asks for login only on clicking other links on that page.