Not the OP but I would guess that there is a large group chat of people talking about something the government doesn't like. The government manages to get their hands on one phone from the group, and then they automatically have all the other phone numbers too.
exact same thing. you register your whatsapp group meaning you either get a mole as a member to keep track of the activities or you are made to (unverified) install pegasus style malware on your phone so that the admins can be tracked.
remember, clubhouse makes you sign up using the phone so there you go. Now, if the numbers werent there, it would still be possible but not as low effort
In much of the world, for the government at least, that is a given: you can't get a phone number without presenting legal ID, and the issuer of the phone number is required by law to maintain this association. This is true in much of Europe, for example.
So what exactly do you think will happen? The government tells signal "We know that simiones phone number is +1 12345678, give us his registration date!"?
