Nice article
How applicable the concepts of decentralisation and federation are to the ATmosphere is debatable, but they are used as an approximation for the core question: how is power distributed in the network? And Bluesky and the ATmosphere make it clear that technological architecture can only help so much here: Sure, you can be completely independent of Bluesky PBC on the ATmosphere, as everything is open. But in the end, 99% of users are exclusively on infrastructure owned by Bluesky PBC. No technological architecture can compensate for that kind of the power distribution.
People interested in actual federation would probably never use ATProto anyway