It is not "perfectly good" if it is undesirable to me that he is eating it.
I don't believe everything I find on Google. However, if I read one post that says something is fine, and another that says something harmful, as a mother I would be inclined to stay on the safe side.
PacMan Dies from coconut fiber substrate [Archive] - Arachnoboards
He also scratches his bad eye when there is coco fiber or duck week in the water, and some of those fibers are longer than his little body.