Well, I disagree, and so does Strunk and White. Why wrap your head about double negatives? We are disposed to complicate things so much, and for many reasons, one of them is to arrogate, another is to mask.
Well, for me, the article helped to unmask, not mask. She was reviewing a book, by Ruse (unfortunate name). In process of that review, she added the Feyerband science-philosophy element, which was helpful to me.
I saw no double-negatives.