Depending on the rice and chicken cut use, you will need to cook it separately if you want the optimal done-ness for both the rice and the chicken.  Optimizing for the rice will result in undercooked chicken, and optimizing for the chicken will result in overcooked rice. After testing the recipe many times, I’ve found that cooking them separately resulted in the most optimal results, and the filter of the stock before cooking the rice allowed for a more-balanced rice flavor.