You might be misunderstanding what Cal Newport is saying here because he agrees with you. He is saying is the people who stay on top of their inboxes and multitask are perceived as being the most productive, not that they are in fact the most productive. He also wrote an entire book that might as well be about his hatred of email titled "A World Without Email," if you need further evidence of his position.
Cal’s writing isn’t clear on where he lands. But he’s probably around to clarify, somewhere. Let’s all send him emails, tweets, etc and see how quickly he replies.
