When Google launched Pixel 4, they allowed the phone to be face unlocked even when the user’s eyes were closed. This was no less than a security flaw as your phone could be unlocked while you are sleeping. Apple who was first to popularize face unlock by default requires the user to keep their eyes open to unlock. Google later promised that they will bring an option to fix this. Finally after five months, in Android 11 Developer Preview 2 update they added a toggle that will make the user require to keep their eyes open to face unlock their phone.
Via - Android Police