Oh. I missed that. In that case wouldn't Confucius grandson (子思) be higher up? After all he supposedly taught Mencius and wrote the Doctrine of the Mean 中庸, and that work is considered standard reading, while reading Xunzi would have been probably only read when you're already a scholar and mastered pretty much everything else.

That said, perhaps the Doctrine of the Mean wasn't considered all that important despite being part of the Book of Rites (礼记), or rather it wasn't considered prominent until around the Song dynasty.