I think they're a bit off on the noise explanation, as they invoke a common misunderstanding of differential pairs on circuit boards (free common mode rejection

I think they're a bit off on the noise explanation, as they invoke a common misunderstanding of differential pairs on circuit boards (free common mode rejection). You're right that differential signals work much better at high speed than single-ended! However one major reason is that you can get a much higher data rate using slower edges by comparing two signals. Diff pair signals don't look more like square waves due to more drive power - they look more like sinusoids. Which uses way less power!