It's a pretty shitty trick to have a "friend" on fbook and unfollow them. I mean, this "friend" happily posts stuff and thinks there are actually people in the universe that might give a rat's fart...but no! They've been "unfollowed". But of course, still "friends".
Bottom-up vs top-down. You unfollowing someone doesn't mute that person to everyone that actually wants to hear from them.