I've worked on a few facial biometric systems in the past and the false positives were really shocking about 65% of them were cross sex and virtually none of them looked alike.

People tend to look at different flesh centric facial features and things like hair style, eye color and overall superficial appearance is what we see. Biometrics see distance between various points like eyes, nose bridge cheek bones etc we tend to actually overlook those fine features when it comes to doppelgängers.

From friends that still work in the field gate analysis seems to have the lowest rate of false positives yet so maybe IPhone X2 will require you to dance to unlock.