It's a different feature. The gist of this new behavior is a change from Allow All Cookies to Allow Cookies Only From Visited Domains. This is unlike Block All

It's a different feature. The gist of this new behavior is a change from Allow All Cookies to Allow Cookies Only From Visited Domains. This is unlike Block All Third-Party Cookies option that existed in both Firefox and Chrome in the way that third party cookie is still accepted but only if user ever visited that "third-party" website before. The behavior may be less strict than Block All Third-Party Cookies option and probably won't make much difference for Facebook or Google's tracking cookies (if you use them). But being the new default option means smaller players going to take a direct hit. Which is good.