Actually, the PIN isn't a fallback - the biometric is just a more convenient option once the PIN is "cached". The biometric doesn't exist until you enter your

Actually, the PIN isn't a fallback - the biometric is just a more convenient option once the PIN is "cached". The biometric doesn't exist until you enter your PIN on restart, which is what unlocks the filesystem (including the biometric profile). You'll also see that you can change your biometric with just your PIN, but you cannot use your biometric to change your PIN.