Technical documentation in this beta feature needs some work. For instance, where is the codebase? I couldn't find it in the beta feature page. I searched everywhere and even I checked collab's people patches in gerrit but still, I can't find the extension that enables such features. Finally, I checked the wikimedia config and realized the config for this feature is "wgEnableRcFiltersBetaFeature" and searched it in github and found WikimediaMessages which has a way unrelated name.
Finding the extension should not be that hard.
And the extension page in mediawiki is comletely empty and looks suspicious (look at the authors)