I agree that the mechanism is elegant, but figuring out which entity should be trusted in a way that scales globally is somewhat difficult.
I can imagine you could share just your DOB in such a case, while keeping your real identity private. In such a way Discord would learn only your age, keeping everything else from them.
Government learns that Discord was provided your data, but this is supposedly a trusted, regulated entity.
In your model, government now know you are on discord -- they know where to ask when they want to find you.
It really depends which government you are under.
But nothing prevents it from being a private company, although I cannot see a sound business model for it. Also it would need to project great credibility for customers to trust them with their information.