I had read the link but not the comment section. I just read the comment section (to about page 4 or 5).

My take on it: Never "Erase" a flash drive. Just encrypt it securely. (I still use Veracrypt rather than Truecrypt (which is now unsupported.)

Because I didn't "know", all my flash drives are encrypted as needed.

Yes, for normal security versus the NSA/CIA/FBI etc., a three pass will do fine. However, you know how picky the U.S. military is, the mil standard calls for 7.

Just as there are many different ways to get access to your sensitive data, there are many different ways to prevent it. Assuming you don't have a leak at either end (NSA watching you or CIA watching your friend), passing a Veracrypted file over an open channel is safe. Of course, since it's encrypted, "theoretically" it can be broken. (Maybe in a few billion years, but....)

However, there are other things you can do that will make a pass through open channels "mathematically" impossible to break. (Even billions of years won't do. Even quantum computing cannot.)

The ABC departments can't break your message if they don't know to even ask. Or, if they do ask, the answer they get is not an interesting (to them) answer. (Look up steganography as well as plausible deniability.)

If I send you a photograph of a horse eating grass on the side of a mountain stream, would the Department of Nosiness really be interested in that? No. But a three part steganograph would give the Nude Communists Political Agenda to you using that horse photo, a one-off code-key (that we both have, and my Nude Communist stuff. (It's a bit beyond the scope of this post to explain the Three Part Steganograph.)

Finally, if you have a video of a nude Richard Nixon boinking Spiro Agnew that is encrypted but deleted and the Federal Boinking Instigators undelete the file, decrypt it, and get Debbie Does Dallas, well, they'd drop the anti-Nixon investigation against you, eh? (Eraser does something similar to that. You can, too.)

Final finally, you can have a Fort Knox level security vault full of gold bullion but if you give the interloper YOUR key to it, well, there goes all your gold. Key-loggers are interlopers. Then, there is the "over-the-shoulder" interloper, the "turning a snitch" interloper, and many other ways to get your gold.

Encrypt your gold. Don't pass it around.