I am not sure that this argument rules out all nudges. The examples he recounts are not really nudges that turn into pushes but pushes from the get go. At the same time, the potential for slippage into pushes should certainly figure into the cost-benefit calculation of whether to have a nudge or not in a given context.
Oh, and if you ever get a chance to have some of David's homemade mead, you should go for it; it is really good.
Hat tip: Don Hacherl