Yes. The government can indeed ask, "Hey, what phone number is 1-555-123-4567 ?" and Signal can tell them it is "1-555-123-4567".
Or, instead of spending $$$ on lawyers to make Signal tell you the answer to obvious questions, which US government agencies have done several times - I reckon I'd do it for $10 per time, minimum order 1000 stupid questions.
I can do other stupid questions, wondering which Telegram user is "@foobar" ? I can tell you it's "@foobar" and for just $10. Now, Telegram can tell you a lot more about this user of theirs, so you might want to get the court to make them do that, but Signal don't know anything about their users so maybe my $10 service is more "useful" for Signal? I guess it really depends what you think the word "useful" means.
