It's that he thinks that the web will win (over app stores). I strongly believe that he's right there.I agree, but not for the technical reasons most people are mentioning so far.
I think there is a much simpler driving force: mobile app stores have set both the quality bar and pricing expectations so low that it's almost impossible to develop good, non-trivial software for them and make money.
On top of that, the app store platforms tend to want a big cut and/or restrict the use of other payment models and/or want developers to jump through hoops just so users can install their application and/or require developers to build in a specific programming language that produces executables for their specific platform and/or a bunch of other obstacles that web development simply doesn't have.
Meanwhile, the only major benefit native apps have to offer in return these days is access to a few native features. Given how much success many web applications have already enjoyed, it's clear that those features aren't compelling in many of the application domains where this kind of decision is being made. It's also clear that if performance was ever really an issue for most web apps, it's an ever diminishing one and mostly irrelevant by now.
The two major business models that have made serious money from mobile apps other than in outlier cases are in-app payments and advertising, which are probably the two most widely abused and consumer-hostile payment models in widespread use today. I suspect mobile apps in their current form were already dead as a serious software platform as soon as people were selling $1 gimmick applications and $5 puzzle games in app stores. The industry just hasn't quite realised yet because there's still too much hype from the (mostly now over) gold rush, but fortunately we have high quality and great value apps like Dungeon Keeper at the top of the promotions screens to show us just how good mobile apps can be if you want to make real money from them.
Meanwhile, as numerous HN regulars can attest, plenty of B2B web apps are making money like it grows on trees, and plenty more people are making a decent amount of money with other B2C business models that simply aren't compatible with today's mobile app world but work fine on the web.