That may be true, but it's not like you can't just re-acclimate to the experience of writing on an iPad. Most people don't handwrite much, period, so if they start handwriting again they're going to have to have an adjustment period either way.
I personally would think that the the benefits of digital writing (searchability, portability, infinite canvas, handwriting cleanup, digitization) would outweigh his friction quibbles. I personally don't find it to be tiring to write on an iPad, even without a screen protector (which some people use to increase friction). Also, e-paper devices tend to have more friction-y feedback, but he doesn't address this at all when dismissing all "gadgets" outright.