People told you a few times to go look for yourself what Signal can give away. Its protocol descriptions are pretty understandable.

The whole bloody reason it's always recommended is because it's absolutely the best thing in terms of yes, encrypting metadata. It's state of the art, level above that bullshit you're thinking.

Unfortunately, that also means that hosting it takes lots of resources, which means they have to screen bots and mults somehow. Phone numbers are one way. Paid accounts are another.