Not to be snarky, but the fact that it has become straightforward to build Sinatra as an extension to Rails is one of the things I don't like about Rails.
The article just seems to be putting Rails 3 design improvements to the test. Personally, I am pretty impressed at how easy it is to swap out Routes/ActionController::Base if you need something leaner or just a completely different approach to routing requests. Remember when we were all banging our heads against a wall with Struts? What's not to like?
You're right, of course, I just think it's ironic that he'd use Sinatra as an example, because Sinatra is what people run to when they get freaked out by Rails complexity.
What's ironic is that the post is meant to appeal to those who always have another "one of the things I don't like about Rails." So your pithy-dig response is just perfect.