If he thinks he is, he is. That's really all there is to it. Reviewing and approving my students' blog comments from my iPhone may not be on the same level as people editing 8k footage on dual-5k displays, but work is still work, regardless of the form it takes or the medium used to complete it.
We are beyond debating whether iPad can be used for content creation. That discussion is over and those still arguing that it cannot are saying more about themselves than about the iPad with every passing month.