Are you saying you can’t have a 4 digit pin? Because if you are then I just want to say that you can have 4 digits if you really want, it just defaults to a 6 digit during setup and there is an option to change to a 4 digit if you want.
Also. Password reuse if a bad thing. If you are really going to reuse a 20 year old pin, you might as well disable pin security completely.