I trust face unlock to prevent my kids unlocking my phone but that's a whole different kind of threat model from a state actor.
As long as you keep the default of requiring attention, face lock is likely safer than a fingerprint from the kid threat vector.
"Fox News reports that six-year-old Ashlynd Howell from Arkansas spotted her mother Bethany taking a nap on the couch. The girl then took her sleeping mother’s thumb and placed it on her iPhone’s fingerprint reader to unlock the device, all so she could order $250 worth of Pokémon merchandise on Amazon." - https://wsvn.com/news/us-world/6-year-old-uses-sleeping-moms...
Bonus: "Face ID shown unlocking for family members who aren’t alike" - https://bgr.com/tech/iphone-x-face-id-hack-family-members/ with the suggestion that Face ID continuously updates the facial features, and by sharing the phone the recognition algorithm may have ended up trained on both faces.
Comments
As long as you keep the default of requiring attention, face lock is likely safer than a fingerprint from the kid threat vector.
"Fox News reports that six-year-old Ashlynd Howell from Arkansas spotted her mother Bethany taking a nap on the couch. The girl then took her sleeping mother’s thumb and placed it on her iPhone’s fingerprint reader to unlock the device, all so she could order $250 worth of Pokémon merchandise on Amazon." - https://wsvn.com/news/us-world/6-year-old-uses-sleeping-moms...
"Cryptographic expert Matthew Green has found his son Harrison bypassing the security measures, CNN Money reports, by swiping the phone with his thumb while he slept" - https://www.dailydot.com/debug/touch-id-child-iphone-unlock/
Though depending on how deeply you sleep:
"Man opens eyelids of sleeping girlfriend to unlock her phone, steals over Rs 18 lakh from her bank app" - https://www.indiatoday.in/technology/news/story/man-opens-ey...
and from five years ago: "Heavy sleepers, beware: Researchers bypass Apple FaceID using glasses with tape" - https://www.digitaltrends.com/mobile/apple-faceid-tricked-by...
Bonus: "Face ID shown unlocking for family members who aren’t alike" - https://bgr.com/tech/iphone-x-face-id-hack-family-members/ with the suggestion that Face ID continuously updates the facial features, and by sharing the phone the recognition algorithm may have ended up trained on both faces.