[unaindz]

That's theoretical only. Nobody has ever demonstrated that since the theory started and now hdd complexity and density has increased dramatically.

[JohnFen]

I had to check with some experts on this that I know, to make sure that I wasn't talking nonsense.

I wasn't, exactly, but I also wasn't correct in the modern day. Retrieving erased information from hard drives like this was certainly a thing (a thing that I myself have seen done, so I know first-hand).

However, after hard drives moved beyond MFM it stopped really being possible.

So what I was saying isn't wrong, exactly, but certainly isn't relevant to today's hardware.