Google introduced the ability to unlock the phone with a voice when interacting with Google Assistant. After being removed on Pixel 3 and Pixel 3 XL, Google might be ending the support and might be finding a replacement on all other Android devices given how insecure the feature is.
“Unlock with Voice Match” allowed users to have their voice act as a device passcode. Even Google considers the feature, less secure as it warns users with prompt warning users that this was the case before allowing you to enable it. Google, with the Pixel 3 and Pixel 3 XL, replaced it with “Lock screen personal results.”
This meant that Voice Match could only show email, calendar, and contacts through the Assistant interface, but any further action would require a password or fingerprint unlock. The Google Assistant features when the device is locked shows a lock icon on top to reflect the state of your device. The Google app V8.39 update includes a reference to a feature dubbed “Updated Voice Match” prompt that details the replacement and that “Lock screen personal results” will be the “more secure way” going forward.
The end of “Unlock with Voice Match” and replacement with “Lock screen personal results.” is not yet enabled as of Google app 8.39. It might change in the future versions or via a server-side update, stay tuned.