I'd say they should use ActivityPub[1] instead of wasting time on their own incompatible solution, but quite frankly I don't want Twitter federating with Mastodon. We get our fill of chuds with anime avatars thanks to Pleroma, and don't really need or want Twitter around because decentralization won't make it any less of a digital sacrifice zone[2].
1: https://activitypub.rocks/
2: https://en.wikipedia.org/wiki/Sacrifice_zone