Probably as in you can move your account to another server seamlessly. Mastodon also relies on "centralised" servers; none of them are p2p

Isn’t that federation?

Just federated identity, like OpenID. It doesn't necessitate distributed systems with communicating backends, like Mastodon or Usenet, just that it allows the user to bring their own IdP and therefore to have "sovereignty" to verify their own identity across platforms. The alternate route is to have users cryptographically certify their registrations post-hoc, e.g. Keybase

You cropped the key part

> ... centralized version and vision