Why is a E-Mail notfication for new registration only possbile when registrations are unrestricted open?

@admins @developers @helpers

I created a semi public friendica instance (kassel.social) and currently I do not want to allow registrations from general worldwide public but from people in my region. For this, I set the registration policy to "by approval".
The problem now is, that I do not get notified by E-Mail if someone wants to register. I need to manually check the instance's front end to see that there is a new registration.
Is this by intention, do I do something wrong? Otherwise, I would like to create a new issue on git regarding this.

Thank you!