Raider.IO is an automated rankings system, and we make use of Blizzard's API to track raid progression to perform these duties. All the ranks you see on the site are automatically computed, and we don't manually insert records.
This works great for all realms, except China, which had their API disabled in 2016. This means that there is no API to access progression data about Chinese guilds, and therefore that we cannot include them in our rankings.
We do care about being able to support China, and are hoping that Blizzard will return access to the API at some point in the future.