In LALA app there is a feature to create pin why it is not a 4 digit pin and other thing that why they have not enabled it through finger print sensor there should be both option as it is easy to use finger print sensor as it would take very less time
Fingerprint passcode is good, and if I talk about my opinion they selected 6 digit pin instead of 4 digits so every profile every user will feel more safe and more secure. I know it is not possible to crack 4 digit code but is more impossible to crack 6 digit code.