Oh! I didn’t realize it only displays on mobile view 
A quick search for site:webflow manifesto gave this as the third link: CMS website builder and design tool | Webflow. This is probably an old page that is not linked directly from the home page or navigation menu, that’s why it was difficult to find.
For the Webflow website’s preview link, see this forum post:
Opening the preview link, you can find one of the page’s slug (url) is cms-website. The preview seems to be cut off as the height is fixed. You can easily see the entire screen by increasing the height of lp-feature to about 1000px.
This is not an actual website, but an animation created to showcase Webflow. However, it can definitely be recreated.