"In other words, he's saying that half of all users don't do ANY searches at all, whereas all that he can say is that on some days, some users don't do any Google searches on their mobile device."

From the article: "who does what searches isn’t fixed; so someone who did zero searches yesterday might do 10 tomorrow. But equally, the 10-searcher yesterday does none or one or four today. And so on."

So yes. But on any given day, half of people don't do a mobile search. And the numbers from Google suggest that the average across a 30-day period is less than 30. If you think there should be a different model for how many people do how many searches than a Pareto distribution, please offer it.