This affects all resources that support extensions but let’s take the User resource as an example:
Extending the User resource currently requires an entire User Profile read/write consent (User.ReadWrite).
We only want to read and write additional data that we provide to the User resource and not modify the entire resource. Users might be hesitant about consenting to Apps that could potentially corrupt their entire user profile.
We do not have this started yet, but its in our plan due to other priorities. ^JT