Good grief, this thread will never end it seems.
The hdparm utility can invoke a secure erase command that is built into the device driver of all hard disk controllers for the past ten years or more. Only the disk drive controller itself can erase the whole disk - including the spaces between tracks. Ordinary software cannot do that.
So if you want to really erase the data (short of melting the disk with a torch) then use hdparm. Any other method is just playing.