A couple weeks ago, we reported how Google has done away with the first click free program and introduced something called flexible sampling. If this is new to you, quickly go read that article.
I did briefly mention the new markup for subscription and paywalled content. But I did not stress that this markup is not required but rather “strongly encouraged” to be implemented by developers on sites that do deploy any form of flexible sampling.
Google rehashed that bit on Twitter saying they encourage the use of this markup for any form of flexible sampling:

We encourage that markup for pages that implement any form of Flexible Sampling. https://t.co/A6U0THR3Mw
— Google Webmasters (@googlewmc) October 10, 2017
So if you are using any of these forms, please review this markup and try to implement it.
Forum discussion at Twitter.