In real life, all you have to do to make "erased data" go away is to
keep your drives pretty full, even if it is just copies of your music
library. If there are no unused sectors, there is no ghost data.
Time is your friend. The more times you overwrite these spare sectors,
the less chance that anything could be recovered, even with the most
sophistocated attempts.
I am sure you are technically correct but again, we are talking about
Hillary Clinton and her concern about what was on those drives. Like
you said, she probably had a hired geek as an administrator for the
server although some times we give important people too much credit.
It would be interesting to talk to the geek with him or her under oath.
Ask what instructions he or she had regarding the remaining data on the
server, what to do with it and how.
Sheesh. You don't need a "geek" to make the data on hard drives
virtually impossible or actually impossible to retrieve. There are
freebie apps that do that, and some inexpensive paid apps, too. Anyone
who can start up a word processor could do it...even you.