A) Is fooled by a phishing attack
and
B) Is not fooled enough to manually copy-paste credentials from their password manager after noticing that the autofill didn't work
Does a person like this exist somewhere? Sure, if you interview 1 million people, I'm sure you will find 1 person like this.
It is very, very strange to me that the security "experts" are narrowly optimizing for this specific user and downplaying all the risks related to their recommendation.