Updated App Store Review Guidelines dictate that apps wanting to make use of Face ID on the iPhone X must offer an "alternate authentication method" for children under 13, notes AppleInsider.
As the article notes, Apple is likely trying to allay any fears from parents, as well as deal with a fundamental limitation of Face ID. The technology will support only one person per smartphone, so mean parents sharing an iPhone X would always have to unlock apps themselves if they relied too heavily on facial recognition.
Apple says FaceID is “even more convenient than Touch ID.” With Face ID, the iPhone X unlocks only when you’re looking at it. It’s designed to resist spoofing by photos or masks. Your facial map is encrypted and protected by the Secure Enclave. And authentication happens instantly on the device, not in the cloud.