Face Unlock via the Soli radar sensor on the Google Pixel 4 is one of its major features, and the device in fact lacks any other biometric security feature.
By default however it ships with one major flaw – the system will unlock your phone when your eyes are closed, meaning a snooping partner (or prankster friends) could easily access your phone while you are sleeping to check your messages and do other mischief.
This flaw is well demonstrated by the BBC’s Chis Fox in his video below:
— Chris Fox (@thisisFoxx) October 15, 2019
Google does warn users of this “feature” when they set up face unlock.
The Pixel 4 can, in fact, detect if your eyes are open or not, but the issue is that by default it does not, presumably to make Face Unlock work faster.
Worse, in Fox’s version, (which he says is running the latest version of the OS) this option appears to have been removed.
If you happen not to find yourself in a trusting relationship, and you plan on purchasing the handset, given that the phone does not have any other biometric security feature, it may be wise to rethink the purchase until Google fixes their unusual decision.