[DanBC]

Wiping drives is one of the weird situations where you can either try to prove a negative ("they cannot recover the information if we do X") or just grind the drives.

Looking just at spining platter drives:

We know that there are no software tos that claim to recover data that has been over written just once.

We know that no companies exist that claim To be able to recover data that has been over written just once.

There are no University projects claiming that either. (There are some obscure projects using onsolete technology that had very low sucess rate for bits).

We don't think any well funded forensic units have had sucess recovering such data.

So, for most people doing a single overwrite of random data is fine.

But some other people need peace of mind, and for those people grinding the drives is easy.