Yeah, I'll try to look into this for clarity. It really depends on what they mean here - I think they're referring to curated server following between admins, which is what PeerTube does.
When I tested out the messaging system, I was able to federate back and forth with Mastodon. Maybe it works fine at a user level, it's just the search entries that don't get federated automatically?
Fucking amazing book, I laughed so hard from start to finish.