[Answer]-How can Django's ContentType uniquely describe an installed model when it only stores the last part of the App's import path in app_label?

It doesn’t matter: when you put 'auth' inside INSTALLED_APPS, only one Django app could be imported, it could be auth from either coke or pepsi, or other place containing auth, depending on their first occurring in sys.path.

Also, in DB, the unique constraint is applied to (app_label, model), the name is for description.