Except it sounds like (from the comments) that it's actually not exactly automated. You have to create the new user account to send out an invite. But the sending of the invite (and the "yes, create a new account") are both triggered by a person.
I have similar things happen all the time, for systems that require credentials. If I never log in, the credentials expire after x hours or days. Unlike the physical keys he uses as an analog, there's no real reason not to create and supply the "key" immediately.