You don't restore your drive, you flash another drive data to yours, essentially cloning the other drive. While that works, you don't actually restore your drive to its original state. Im not sure what hddhackr backs up, but if its the firmware - every hdd firmware is unique to its drive, based on the plates, P/Q lists etc.
correct you simply restore the drive specific information overwritten by hddhackr
it does restore the drive to the original state albeit with a different serial number, does it really matter as long as it works in a PC/MAC?