This is about specific sites' abnormally high methane pollution, and China is in the data set but does not have as many "super-emitters" according to this. Here's an example where China's listed in the linked Sky article:

Coal is also a problem with one facility in Shanxi, China, peaking at around 181 tonnes an hour last February.

However, they go on to rank the countries in the article as such:

Kayrros's data shows Turkmenistan had higher methane emissions than any other nation, followed by the United States, India, Russia and Pakistan.

So the answer is simply that China, along with the EU, does not have as many "super-emitters" to worry about. Other regions do, and that means they can target those sites specifically to reduce their methane emissions now that the data clearly highlights them.