Earlier quoted context omitted.
Okay, so there's two requirements for any legit authorization to pass: identification, and authentication. For Unix accounts, the username is the identification bit, and the password is the authentication bit. Now, you don't usually type the username when you run sudo, do you? That's because most of the time, the username can be gleaned from context. For example, "Which user is this process running under?". So, if To…
I agree. But my thinking is that touch id just shows who the person claims to be (like a username), but it doesn't actually authenticate they are that person. I know that in practice apple does use it to auth.
It's a "something you are" authentication factor, since it is presumed that the cost of faking a fingerprint is too high to be worth it in those cases.