My guess is that the way the fingerprint sensor is so damn fast is that it's active 100% of the time. So when you touch it and press it, it's already registering your fingerprint before the display even turns on.
Maybe some kind of bug is causing the fingerprint sensor to malfunction and temporarily make the phone unusable until a hard reboot.
Maybe some kind of bug is causing the fingerprint sensor to malfunction and temporarily make the phone unusable until a hard reboot.