I guess using the bathroom isn't being 100% efficient either. Neither are coffee breaks, smoke breaks, talking to a co-worker, drinking some water or doing some research/checking web dev news that is related to your job. There is no way they can ever get a person to be 100% efficient, I think Paul Graham was right about some of these stories in the media (like how "suits are back") are nothing but propoganda to try to influence the work environment.