If I understand it right, this is a feature developed from inception on Piefed. I’ll just say it here: it’s like multireddits. They have default comm group feed, at least on piefed.social. But you also can make your own group feed. Just like multireddit.
I personally would move to a piefed instance once it’s more developed and have more choices for front end client / mobile app, since that’s the biggest thing I miss from reddit.
Edit: and IIRC piefed also group same posts from different duplicate / similar comms into one “post”.
Would be lovely if you have some source or something to read about.
Consider my interest piqued. I gave the Wikipedia page a skim and it seems like a good starting point