How to remove the confirmation step in the PIN unlock screen? I’d like to remove the need to press OK or ✔️ for a faster PIN-unlock, the confirmation step doesn’t add any additional level of security since it seems the PIN length is always 4 digits.

I have currently have Android 5.0.1



As a side note, I’d like to know if having a PIN longer than 4 digits is useful somehow. I’d bet the great majority of users use 4-digit PIN numbers. Also discovering the length of the PIN because of the confirmation step being removed shouldn’t be a problem because entering the wrong PIN number several times should trigger some alarms in the operative system to do something like wiping all the data or reporting the incident to someone. Maybe that's why ATMs use only 4-digit PIN numbers, if you want more than that there should be an additional option for alphanumeric passwords and that should be it, I mean not for ATMs but for mobile devices.
Stock android does not have the ability to disable this feature, as such it requires you to confirm the PIN every time you enter it. Depending on your phone, the version of Android on your phone may support this functionality. 

I believe this functionality is also part of CyanogenMod (It was when I ran it a few years ago). 

Also, PIN's aren't always 4 digits long, stock Android requires PIN's of at least 4 digits. Automatically confirming the PIN after x digits would kinda defeat the purpose of a longer PIN because you could find out the correct length in one attempt.