Even ignoring that substantial problem, dd also tends not to work when the hardware is broken. (And you can't be sure it's sufficiently broken to prevent data recovery.)

Yes. Incidentally when you get a nice fresh SAN for example, you can dd 20TiB volumes in a couple of seconds. Doesn't mean they have been written to.

> Second, overwriting the entire visible address space of an SSD twice is usually, but not always, sufficient to sanitize the drive.

Overwrite you whole SSD 10 times I doubt anyone but the most serious attacker can find anything, and even then.