> Do they determine that people just take more sick days because they need some level of privacy

Yeah, I too think this could explain it better. Say a work day is 8 hours, ideally, you cannot work on the same thing for 8 hours. But an open-plan office forces you to do this, or pretend to, because you are being "watched"...and this can be exhausting.

A cellular office plan, gives you the privacy to relax, and maybe do something else, then say when you feel refreshed, you get back to working.

An open-office plan encourages collaboration, but that's based on the assumption that we all work the same way.