is_user_logged_in() returns true even if user is not logged in

[TomAuger]

If you have wp_set_current_user(), then is_user_logged_in() will always return true. This goes against my understanding of the role of wp_set_current_user() especially as explained by the documentation:

"Some WordPress functionality is based on the current user and not based on the signed in user. Therefore, it opens the ability to edit and perform actions on users who aren't signed in."

But then we look at is_user_logged_in() and it just says - can we get_current_user()?

Suddenly wp_set_current_user is looking like wp_switch_logged_in_user(), which I doubt is the intent of that function.