frunny,
We’ve got social login working for facebook, google and apple. The first year we used auth0 it was just standard username/password. Adding social brought some twists - users who socially login have an account in Auth0 for that, users who login via username/pw have an account.
If you examine users created in your tenant using each method, social vs un/pw, you will see the user id: value changes. Users created with un/pw start with auth0|, where facebook starts with facebook|, apple with apple| and google with google-oauth2|.
The “sub” subject in the JWT will also display this user id value.
Hope this helps!