I don’t have any data or specific research, but you can consider that everything is getting faster: internet speed, servers, and client machines. Maybe this can make some of the optimizations irrelevant for most applications.
From the article, what I mostly agree with is that Turbo Drive does a lot of things that the browser already does, but I think that faster navigation isn’t the main point of using Turbo Drive right now; it’s a bonus.
Good point, I didn’t realize he was using localhost, I just noticed the simplicity of the application.