Whos wrong?

Boyfriend of 6 years says its ok for a guy to not have any relationship status or any mention of his girlfriend on facebook because he has mostly coworkers on his facebook and they dont need to know. Coworkers are on there for communication. He said to keep work and private life private. I say thats ridiculous and if his coworkers are on his private facebook page then thats already merging private with personal and making them more of an importance and hiding the girlfriend. He just keeps saying its none of their business. They share everything else and talk about everything. Why is it a secret