Is it? Do you have pages that don't include assets? No JavaScript? No CSS? No images? If so, then I think you're right. Otherwise, built-in Rails functionality will make all your pages faster.
All of the speedup suggestions outlined in your article can also be handled easily - easier than Rails or not, I don't know - in other languages and frameworks as well. There is nothing about any of these items that only Rails can handle - heck half of them don't even have anything to do with your choice of server-side frameworks.
The main point of your article is "How Rails can make it easy to make your pages load faster".
Looking at http://www.alexa.com/topsites for example, which of those would you think Rails could make faster?