For phone-based biometrics, the PIN has always been a backup for the fingerprint/face recognition, because these things aren't 100% reliable. Not even consideri

For phone-based biometrics, the PIN has always been a backup for the fingerprint/face recognition, because these things aren't 100% reliable. Not even considering any security aspects here, just practicalities, like your hands are dirty or your face isn't being recognised (perhaps you've got bandages on your face or whatever). Having the PIN as a replacement is a good thing in these cases, otherwise you could be locked out of your device when you actually want to use it. For 'extreme' security situations, you might as well just have a long secret PIN and no biometrics.