This feature is a lifesaver for fediverse. It allows you to see from a general perspective, reduces confusion and creates a more organized forum environment. Thank you to everyone who has already used this feature and I highly recommend everyone to use it.
AFAIK, the grouping is done by the API only when you’re viewing a post and by the UI when you’re browsing the feed. Unless 0.19.4 changed this, the call to list posts doesn’t return crosspost data and it has to be done client-side. I’ve grumbled about this a lot lol.