iPhone X owners have found that Face ID isn’t available as an
authentication method for the “Ask to Buy” feature, which allows
parents to approve their kids’ iOS purchases and downloads.
Instead, the parent (or any other “family organizer,” as Apple
terms it) must enter their entire Apple account password to
approve each individual purchase attempt.
Users are frustrated because equivalent functionality was
available on Touch ID devices, and that functionality has been
lost in the transition to the iPhone X. Face ID can be used as an
authentication method for other purchases, just like Touch ID
before it — but Touch ID also worked for “Ask to Buy,” and Face
ID doesn’t. […]
Parents of large families with several children, each of whom
might have an iOS device available to them, will find that the
requests mount up quite quickly — especially right after the
holidays. Kids cashing in App Store gift cards add to the requests
already coming in from normal use and in-app purchases in games.
I only have one kid, but I noticed this too in the post-holiday gift card bonanza. I can’t really think of a good explanation for why Touch ID can authorize these transactions but Face ID can’t.