The security is based on the premise that Apple is unable to decrypt as they do not keep a record of the devices unique ID that is the base of all the cryptogra

The security is based on the premise that Apple is unable to decrypt as they do not keep a record of the devices unique ID that is the base of all the cryptography. What if that is not true? What if the device has a built-in keylogger to just get all the crypto from the user input? be it a passcode or a fingerprint. Wouldn´t it be partly better if this were based on a trully public key cryptography with a randomly generated private key generated each time the device is factory reset?