Muting isn’t restricted to followers. It means that your activities don’t appear in the activity feeds for you, your followers and everyone else. What you describe sounds more like this idea you could vote for:

If the thread starter is asking to suppress some of his activities from appearing in the feed of a select group of his followers, then this is the appropriate topic to vote upon:  

https://communityhub.strava.com/ideas/privacy-add-more-options-for-choosing-which-followers-groups-clubs-to-share-activities-with-6716

Always open to correction, but that's how I read his question.  (So your boss doesn't know you took that three hour lunch break!)
 

​@JBW-Florida Yes, that maybe too, my post refers to the “others don’t want to see” and “vice versa” in the OP.