1) you can move your identity from the gitgo. Yeah, sure, AP allegedly allows this, but your are at the mercy of the server owners to cooperate. Assuming, of course, the server even is still reachable. And even then, recent (last 5 months) there are numerous examples of transfers failing badly.
2) This protocol doesn't force you to trust that the server admins aren't reading your messages. This is not the case with AP.
3) The relay system, whereby to get notices from other communities, is wildly broken, and the two largest Mastodon servers don't even support them.
I'm as skeptical of Mr. Dorsey as anyone, and the community absolutely deserves the right to see deep into this protocol. That said, implying that Activity Pub meets or beats everything this new protocol offers is not correct.