Obviously I can’t speak for Colin Percival, but I think that the point of the article is quite a bit simpler:
I read this as saying that the mindset required to write proofs is similar to the mindset required to write secure software. The proof mindset is useful for considering “all the real-world ways that things could go wrong.”
I think the paragraphs about Knuth’s famous quote just muddy the water.
My point wasn't intended to be as low-level as it came across. Perhaps a more clear restatement is that I suspect that the attention to detail that I associate with the "proof mindset" isn't quite the same thing as the "twisted mind" that Bruce Schneier talks about; so I'm not convinced mathematicians are more likely to have that skill.
I read this as saying that the mindset required to write proofs is similar to the mindset required to write secure software. The proof mindset is useful for considering “all the real-world ways that things could go wrong.”
I think the paragraphs about Knuth’s famous quote just muddy the water.