That tool, apparently, just attempts to write zeros to every mapped sector on the drive. Which works, most of the time. So it sits there, in a loop, writing 512 zero bytes at a time, until the entire drive is accounted for. The Linux equivalent (free) is simply "cat /dev/zero > /dev/sda". Except this program deliberately slows itself down unless you pay the ransom.

What a SECURITY ERASE command does, is tell the drive to format itself, which will always be better / more reliable than some hokey program writing zeros. Since the drive itself is doing the format, it runs at full drive media speed. As fast as the mechanism can do it. And with full knowledge of defect management.

Cheers!