If a device supported and was provisioned with both, and unlocked with either, you would have double the potential for biometric attacks/vulnerabilities (rememb

If a device supported and was provisioned with both, and unlocked with either, you would have double the potential for biometric attacks/vulnerabilities (remember that FaceID is an order of magnitude stronger biometric). If you support just one with the other disabled, it is wasted hardware/space in a device with extremely limited size/cost budget. If you require both, you haven't fixed the usability issues.