He is simply listing the challenges any designer would face to make a simple yet obvious feature that just works. It is NOT describing a reason to "go back to buttons" or do something in the traditional way. This is where home electronics need to go - where you can interact with them directly instead through some button interface. If I direct my phone at the TV, both the phone and the TV should know that this is happening and depending on context, do something or offer a choice. Another example is touching your phone to your computer, etc.
The challenge, apart from making the design intuitive, is for the devices that take part in this form of interaction to understand the intent of the user.
What is wrong with having the user say what they want? My microwave doesn't popup open the door and grab what I am holding whenever I pass food in front of it, and that is fine.
If the gesture is intuitive and simple, it can be much more efficient than a button and reduce cognitive load by eliminating symbolic abstraction.
A great example is browsing in Safari. Scrolling, zooming, and going back/forward with gestures is far more efficient than explicitly pressing buttons to do the same actions.
The challenge, apart from making the design intuitive, is for the devices that take part in this form of interaction to understand the intent of the user.