I'm not an expert but i imagine bio data being much less exact than a password. Hashes work on passwords because you can be sure that only the exact date would allow entry, but something like a face scan or fingerprint is never _exactly_ the same. One major tenant that makes hashes secure is that changing any singlw bit of input changes the entirety of the output. So hashes will by definition never allow the fuzzy authentication that's required with biodata. Maybe there's a different way to keep that secure? I'm not sure but you'd never be able to open your phone again if it requires a 100% match against your original data.