Session data after login

[yuanlu0210]

From the book, I read "When users log into the site, their anonymous session is lost and a new session is created for the authenticated users. If you store items in an anonymous session that you need to keep after users log in, you will have to copy the old session data into the new session."

which seems to be different from what's in the Django documentation:

"Note that any data set during the anonymous session is retained in the session after a user logs in."

(See https://docs.djangoproject.com/en/3.2/topics/auth/default/#django.contrib.auth.login)

Can someone help explain this? Thank you!