Ohhh totally forgot about that. Apparently they wanted to do their own thing or something. Doesn't make sense to me. I'm on lemm.ee so I can sub though
The defederation is one-way; lemmy.world isn't defederating beehaw.org. lemmy.world users can still see the community, and even still post to it (I assume, not sure if lemmy.world took changes to stop that but, as you can see it even has posts from local lemmy.world users as of 2 months ago, but the last content from anyone outside the instance is 7 months old). However, they will never make it to beehaw.org and thus won't be federated anywhere else (only users on lemmy.world would ever see it).