The advanced pin in the android app to block uninstallation and power off will allow you to set a pin with more than 4 digits, but then the unlock screen will only allow you to type 4. This completely locks you out of your phone, until you wait for the battery to run out and shutdown the phone.
On the settings page before you set the pin it says “set your 4 digit pin” but then when you actually go to set the pin, it doesn’t say that and it also doesn’t have any checking for length, so I set a 6 digit pin and stored it in my password manager.
This then gets reported as a 6 digit pin in the settings (so it saved the whole pin), however the unlock screen will not accept any more than 4 digits.
I suggest that you either block anyone from being able to set up a 6 digit pin, or you allow them to enter more than 4 digits in the unlock screen, because locking someone out of their phone completely even when they know the pin that they set is a really bad user experience.