Beehaw has good intentions, but I don't know if those intentions are entirely compatible with the fundamental architecture of Lemmy.

They literally are because being able to defederate is part of the fundamental architecture of fediverse apps.

Yes, but in their post they wrote about how the large influx of users from other instances made their specific goals too hard to accomplish.

It wasn't a philosophical difference with lemmy.world, which is a case that federation would have worked well with, it was simply that there were enough new users that they couldn't maintain the tighter moderation that they want. And that's fine, they have the right to administer their instance however they'd like, but if they are having trouble with new users from lemmy.world then they're going to have trouble with any federation with enough cumulative users.

The main issue with an instance such as lemmy.world is that they don't vet people at all. Beehawk manually approves their users, but that becomes kinda pointless when anyone can just create an account on lemmy.world and then go post on beehawk.