Weird. It's fast on my Thinkpad X201s from aeons ago (running chromium).
When I click the last page button on the right side, it runs smoothly through all animations, same when happens when I scroll around. Can't wait to see someone make a blog post on: "This is how Sony exploited HTML5 to run Smooth Parallax Effects on their Page".
I ran it in Firefox with about ~100 tabs open having over a dozen addons, an IDE opened and npm install running in the background.
tips fedora
It's quite a simple and elegant way to do it, other than the incredibly large number of images required to pull it off. You are essentially watching a video frame-by-frame.
As for the smoothness of it, your mileage may vary based on various things to do with your personal setup.
For me it is not smooth on Firefox. It's choppy but still presentable. The experience is much better in Chrome on my Mac.