The Wired article doesn't make clear the reason for using humans rather than a mechanical generator of randomness, hence several commenters here are, understandably, questioning this. Why not use a chaotic physical system instead? Because that would involve assumptions about the behavior of the chaotic system. A way to eliminate these assumptions is to add "free will".

Original paper:

https://www.nature.com/articles/s41586-018-0085-3