The Ritsuryo system was completed after the Taiho Ritsuryo and it is highly possible that Taika Reforms were described in an easy-to-understand manner in "Nihonshoki" in a way to overlap with Taiho Ritsuryo.
律令制度が完成したのは、大宝律令からであり、その大宝律令と重ね合わせて解りやすく『日本書紀』には記述した可能性が高い。