It is just the same old stuff with username & password combination. I used to duplicate websites, they looked exactly like the original, except I was storing the entered username and password combination. I did this when I was a kid. The process is the same (or very similar) with everything else that is not a password.

True, they do it to facilitate access to their site without a password, but personally I don’t like getting an email just because I entered my username to sign in (my password manager takes care of filling the form so that email with a code is unnecessary to me).