This article on Techcrunch.com (and direct confirmation from Samsung) seems to contradict that...
https://techcrunch.com/2017/09/06/dont-rely-on-face-unlock-to-keep-your-phone-secure/
In fact, the company likens the feature to a simple swipe to unlock in a statement given to TechCrunch, “Facial recognition is a convenient action to open your phone – similar to the ‘swipe to unlock’ action,” the company says. “We offer the highest level of biometric authentication – fingerprint and iris – to lock your phone and authenticate access to Samsung Pay or Secure Folder.”
Samsung’s been fairly transparent on the matter. A visit to the Security tab on the Galaxy S8 page, for example, notes by way of an asterisk that “Face recognition is less secure than pattern, PIN, or password.” It’s also worth noting that there’s a “Faster recognition” setting hidden behind a few menus (including the ominous message “Your face has been registered”). Turning it off “increase
security and make it harder to unlock using an image or video.”