I am currently the admin for an AAD B2C tenant (I can add B2C applications, flows/policies, etc.) but I can view only some AAD stuff. I understand that AAD B2C is a different service that is somewhat under our organization's AAD umbrella, but I don't have access to the AAD configuration.
I noticed that all the AAD B2C users are also shown as AAD users, and any new B2C app automatically appears in the App Registrations on the leftmost blade in the Azure portal.
All these make me think that AAD B2C uses AAD underneath. This is indirectly confirmed by the existence of a special application registered with the AAD (named "b2c-extensions-app. Do not modify. Used by AADB2C for storing user data."), which serves as a bridge between the two.
Does anybody know any more details about this relationship? I searched a lot but couldn't find much about it.