>I thought it's settled science that polygraphs don't work

Of course they do. And if you read the article in the OP you also realize why.

Polygraphs are an interrogation tactic, you can force a subject into a somewhat ridiculous procedure and ask them threatening questions, creating an disorientating situation. Afterwards you can accuse them of having "proven" that they are a liar. Polygraphs work, it just does not matter whether the machine is on or off.