Earlier quoted context omitted.
That’s only phone number privacy from other users. Registration would still require a phone number, which is what GP seems to be unhappy about.
I don't see the point of all that encryption when the ends of a conversation are tied to publicly available info like a phone number. Do you think $SECRET_POLICE will care that they can't decrypt my messages when they know I have exchanged said messages with a known dissident's phone number? $SECRET_POLICE doesn't do innocent until proven guilty.
Also, dissidents aren't the only (and definitely not the primary) intended users for Signal