It would be more surprising (to me) if Facebook were monitoring hiding things in the news feed - they're a database query away from knowing what you've unfollow

It would be more surprising (to me) if Facebook were monitoring hiding things in the news feed - they're a database query away from knowing what you've unfollowed. Knowing what's hidden is an active request back to the server to report which elements now have been hidden. The other side is that things that are unfollowed aren't ever sent to your browser...