Comment by greyface-

It's a great encapsulation of why Signal is not federated, and, unless you find the current CEO stating otherwise, is unlikely to change. Changes like the one detailed in the link simply wouldn't be possible to roll out efficiently in a federated ecosystem.

Signal has consistently focused on helping /most/ users do what they want with the app without sacrificing security. This change - away from requiring phone numbers - helps plug one of the biggest criticisms, both on the security and product side. Nothing about their mission requires federation, so I respect that they haven't sacrificed their mission in order to do it.