So does Android. You should definitely add fingerprint scanner to the device unlocking field then.IOS requires the user to tap in the PIN upon startup. Once done it accepts the fingerprint scanner as the primary mode of authentication for subsequent unlocks.
Actually other than post start-up PIN (which is used just once) the fingerprint scanner is the primary method of unlocking the device including for apps such as the App store, password managers etc. More convenient than typing out complex passwords.So does Android. You should definitely add fingerprint scanner to the device unlocking field then.