I know there must be a reason and I’m late to the party, BUT…
Why is there a pin screen/login? (And lets not confuse SIM PIN with phone PIN/login.) Why not username and password - at least for first login at power on (or is it like that)? Pin for lock screen only is more understandable, but I’m not sure if that is what is meant.
… and that is only a segway to my actual question: could numpad be randomised, so that fingerprints or identifiable movements can not be used to quess PIN? These are some of the easiest ways (with or without a camera) to obtain it.