If you use “OK Google” the function will change. Google removes the "Unlock with Voice Match" or "Unlock with Voice Match" feature, making it much safer to use.
Right now, using it operation “Ξεκλείδωμα με φωνητική αντιστοίχιση”, μπορείτε να ξεκλειδώσετε την device by saying “OK Google”. 
Although this particular one feature it's very convenient, it's also a very big security risk. If someone else's voice sounds like yours, then they can very easily gain full access to your device.
As it seems, Google removes this feature from all devices with Android. It started with the Pixel 3 and 3 XL, but confirmed that it will remove the feature on all other devices with Android, and the Moto X devices and pixel XL will be one of the first devices that will lose this function.
Of course, with this increase in security, there will be at least one loss in functionality, but it seems worthwhile.
Devices will continue to be protected by PIN, pattern, passwords, or some biometric verification.
