Right, I'm not sure the author understands key either. It's an optimization to help React identify insertion / removal / reordering of array items between re-render. https://beta.reactjs.org/learn/rendering-lists#where-to-get-...

Giving every item a new key on every update does not help with that - in fact it is likely strictly worse than just using index since it will cause every item to re-mount every update https://beta.reactjs.org/learn/preserving-and-resetting-stat... which is unlikely to be what you want.