It's a very long post, but a lot of it is a detailed discussion of terminology in the appendix -- no need to read that unless you're into definitional struggles.
Agreed that Bluesky's run by a single corporation so it's different than today's ActivityPub Fediverse, but the Fediverse's historical approach to "open federation" isn't the only approach. Even in the ActivityPub world we're seeing more and more experimentation with allow-list federation.
For people who want to join a twitter clone there aren't any good ActivityPub options -- Mastodon's good at other things, but isn't a good Twitter alternative let along clone. And ActivityPub's version of "true federation" isn't the only kind of federation. That said, I agree that AT isn't an option for people who want to join a federating-in-theActivityPub-sense-of-the-word Twitter clone,