If he's concerned about privacy of data he should scrap the hdd. Either way on the hdd or formatted those can be still recovered. If hdd is cold then you don't need to worry about it, they'll scrap it for customer and won't try to recover any data.
While if he asked for recovery of data, well that would lead cops onto him; as they are forced to disclose any copyrighted material back to authorities.
If the drive is till partially working you could try a "0 format" on the drive otherwise, the factory most likely go through thousands per day and could care less about the contents of the drive. On a final note if hes that worried about it maybe he shouldn't have been doing it in the first place it sounds like a guilty conscience to me.
Oh the drive doesn't even spin, I dunno what exactly is wrong with the PCB, can't find a replacement part. It seems like this drive has had this issue from what I've read on other forums, I just advised him to not buy seagate again and gave him another drive and turn them into book ends.