Why does that even work? I get technically what is going on - WSJ see the link as having been referred from Facebook. But why does the WSJ display the content

Why does that even work? I get technically what is going on - WSJ see the link as having been referred from Facebook. But why does the WSJ display the content for free to somebody that seems to be coming from Facebook yet look for a subscription for direct access (or from a Google search result referral) .