Their reasoning behind why ActivityPub doesn't meet their expectations is funny, too. They're basically saying "it relies on DNS and servers, which means it's centralized identity". Yes it is. And no, I've yet to see a fully decentralized form of identity that's actually suitable for the real world. Email is also "centralized identity", and it also relies on DNS, yet somehow it survived for 40 years and is still an essential part of the internet.
It’s basically impossible to be fully decentralized. Even if we’re sending around IP addresses to each other, they’re still attached to your ISP. Federation and decentralization aren’t the same thing (which I’m sure you know), so I think we can agree that Twitter’s rationale is mad gay.