I also noticed this for a time. I guess 9pF is mostly like the load capacitance value and I always use it to calculate the proper capacitor value. I used a agilent 53131A to measure the accuracy and the results were ok.
As of why it's not appearing in the datasheet, I believe it's because YXC is lazy on writing a detailed datasheet and just use a simple single version of datasheet for different frequency products of the same series, which have different load capacitances. They might provide the load capacitance value in another way together with the purchase order, and LCSC wrote it on the product page.
As I mentioned, it's a guess, I have no solid proof. But there are many unprofessional practices like this in many companies, which I hated very much as a Chinese.