Corey Doctorow didn’t invent that term, but I’m glad people are talking about it.
It comes from “centaur chess” which is chess where both players are assisted by a computer. The humans are “riding” the computer in the centaur analogy — benefitting from the computer’s ability to process the best tactical move, while the human handles the strategy. They found out that computers win chess against humans every time; but humans with computers win against the computer every time.