Destroying the encryption key tends to be the only reliable way to put the data beyond use. Physical destruction techniques like the obe in the article have been tried before, and iften leave the data intact, just destroying the driver side of the chips. It's not easy to retrieve the data, but a sufficiently determined and resourced oppinent can do it.

Obviously, there's no reason not to do both, for added certainty, but if the encryption protocols used in proper FDE are compromised, we have a lot more to worry about.