I emailed IANA (Internet Assigned Numbers Authority) earlier today to ask about the new content on example.com. To my surprise, their VP replied. Here is the email: I am happy to try and answer any questions you have. The changes we make to the site from time-to-time are usually informed by a desire to either reduce the overall bandwidth demands of serving the site, or improve its utility. At its heart it is a placeholder...
So basically what is happening now. The JS allows it to happen on the client side, taking a HUGE load off the server trying to parse the ua string, find the right translation, bring up the file, and respond. They probably have a single binary that has the HTML, CSS, and JS all compiled in and update it once every year.