Systems containing software fail, and the cause of that failure may originate in software.
And the article you intended to link is just wrong. E.g. the Therac-25 was not designed to output high power when an operator typed quickly; it was built in such a way to do so. This would be analogous to describing an airplane failure due to using bolts that were too weak: "the bolt didn't fail; it broke under exactly the forces you would expect it to break from its size; if they wanted it to not break, they should have used a larger bolt!" Just like in the Therac example, the failure would be consistently reproducible.
And the article you intended to link is just wrong. E.g. the Therac-25 was not designed to output high power when an operator typed quickly; it was built in such a way to do so. This would be analogous to describing an airplane failure due to using bolts that were too weak: "the bolt didn't fail; it broke under exactly the forces you would expect it to break from its size; if they wanted it to not break, they should have used a larger bolt!" Just like in the Therac example, the failure would be consistently reproducible.