It's gets even more comical: Mastodon is just one server implementation of the ActivityPub protocol. Pleroma and Misskey are other ActivityPub implementations. Moreover, all ActivityPub servers make up the Fediverse.
So, this new policy is free-reign to say stuff like:
  • "here's my activipub account: @orthzar@liberdon.com"
  • "I'm on the fediverse at ..."
  • "I have an acount on this pleroma server ..."