Starting with version 5.10.3, if the hard drive is locked with a hard drive password, it can be still erased, but the user must provide the correct password upon booting the machine.
Note that password locked drives can be only erased with erasure standards containing traditional overwriting rounds (such as Aperiodic random overwrite). The password protection prevents executing any firmware based commands onto the drive. If it is required to have purge-level erasure result, the password protection must be removed from the BIOS/UEFI settings.
If the drive is password protected, there will be a red password icon displayed under the drive details in Drive Eraser user interface when in Advanced-view.