Azure AD B2C MFA Email is deleted after phone number is added in custom ploicy

Question

When setting up new registration for users, using application, we are creating users into B2C. Into the B2C tenant that users appearing with their email address as authentication method only. When you try to sign up (into the application) with the newly created user you are asked to set up authentication method and when you select phone number and set it up correctly into the sing up process the authentication method is updated correctly into B2C(the phone number) but the email address is being removed. On the other option for using authenticator app for the authentication method and it is selected and confirmed the email of the user remain as authentication method into the cloud(the B2C tenant)