Gruber's take in that link is curious: does Bluesky lack the concept of defederation (yikes) or is he just assuming that even though Bluesky markets itself as "decentralized" almost no one will actually use it that way?
My hunch is the latter, and that he's intuiting what's going to be an important differentiator between Fediverse apps and their diversity of instances vs. how the AT Protocol is likely to be used in practice: as a shuttle between walled gardens.