The 9-year-old in question was savvy — pointed the phone at his grandpa and unlocked the device. Didn't force anything.
The grandson, however, would be hard pressed to get grandpa's fingerprint without his explicit cooperation! He certainly couldn't “force” him to do it.
So, in that case, Face ID is definitely less secure! 😎
Picture a pickpocket or hold-up in winter… they could grab the phone and do exactly what the youngster did. Quick and easy. However, getting someone to take off their glove or mitten, ensuring their finger is lined up on the Touch ID scanner, and confirming that it worked would take time. It would draw attention, or could lead to the phone being grabbed back.
So, even in that hypothetical, Touch ID would be more secure…
OTOH, given that many feel that Face ID is less accurate, and on older phones doesn’t work if the owner has a mask on, that could make *it* more secure! 😎