And to be clear, it’s like those apps that just fence a website into a fullscreen WebView container. It’s the same forum, still in a Chrome tab, that just has all the excess Chrome UI stripped out. This has upsides and downsides (maximum viewing area / minimum distractions, but no tabs or, say, browser plug-ins if you use a non-standard browser normally).
I do exclusively use the appified site, and as a bonus, I can add the little shortcut it made out of the site icon (the thing that got weird looking in PG’s phone update) right on my home screen.