Windows allow the users to log in to their profiles using either a Numeric PIN, a Fingerprint or Facial recognition. In order to use these features, the user must first set a password for his profile and then he will be able to enable one of these features. By enabling these features the password is getting overwritten by the corresponding new credentials.
The Robot is using this password to log in and it is bypassing the selected feature (Numerical PIN for example). So if the initial user password is provided to the Robot, it will auto-login successfully.