Just looks like a static version of the devforum held on a CDN. You’ll find similar for most sites that use CDNs to host static content. Nothing secret or special.
There’s nothing wrong with that. What happens is that you get that when you simply disable JavaScript on your browser. As said - nothing secret, nothing special, not an “intended change”, just the barebones site - to Discourse’s credit, however, it still works as humanly as possible. You can read a topic from down to bottom. You cannot post (I think) because that mechanism relies on the feature you just disabled.