Basically, iPhone X users are unable to use facial authentication with the "Ask to Buy" feature, which lets parents approve their kids' iOS purchases and downloads. On iOS devices with Touch ID, parents – or "family organizers", as Apple calls them – can use Touch ID to approve Ask to Buy, but iPhone X owners are forced to enter their password manually on every occasion, which could quickly become a nuisance for device owners with big families.
The inability to approve family purchases with Face ID is noteworthy, given that Apple has marketed it as a functional like-for-like replacement for Touch ID, but with enhanced security and speed. The frustration surrounding the missing functionality appears to have come to a head only recently because of the popularity of App Store gift cards over the holiday season.
Face ID is generally very secure in everyday use cases, and while some attempts to fool the feature have been successful, many involve complicated technical methods and a good deal of preparation.
That said, we have seen evidence of a 10-year-old child unlocking his mother's iPhone X with his face, even though Face ID was set up with her face. Apple itself also notes that Face ID often fails to identify between identical twins, while the probability of a false match is higher among children under the age of 13, because their distinct facial features may not have fully developed. These caveats have led some to speculate whether Apple is erring on the side of caution in choosing not to deploy Face ID for family purchase approval.
In early 2013, Apple settled a class action lawsuit originally filed by parents after their children ran up hundreds of dollars on in-app purchases in freemium games. In 2014, the company entered into an agreement with the Federal Trade Commission, promising to provide $32 million in refunds to parents whose children purchased unauthorized in-app items.