Hello @Amy Z ,
When I tested at my end by following the article API Management with AAD
I observed that only email was not getting pulled up, hence in the sign up page appeared to enter in the email.
For email to be returned in the AAD Authentication, you can follow the below steps :
In the App page ( Azure AD --> App Registration --> Your app for the AAD Login --> Token Configuration )
This is the App that you'd have registered as per the above article.
You can click on the "Add optional Claim", Token Type -> ID , select the Email, click Add
You will be informing the App to return the email as well in the token. Now, the sign up page will not appear as all the required information are now returned post the AAD Authentication.