DHH, the author of this post and Rails itself, is and has been actively campaigning against client-side applications, as they clearly undermine his server-side ecosystem.
I'm happy they continue to support methods like this though because I REALLY enjoy being able to put up a site that works perfect without javascript, gets crawled by everything and has a fantastic user experience for people with JS without having to worry about duplicating "MVC logic" on both sides, messing around with having to render something in 2 different template languages or add a lot of extra boilerplate.
Everything just works and is lightning fast.