You've got to be kidding right? Are you really surprised that an English language site that is sometimes blocked in China and lacks a Chinese language interface doesn't have obviously Chinese contributors? Do you expect a conical hat on the profile pics of all the Chinese contributors? How exactly do you expect to see who's Chinese and who's not on a site like Github?

You can easily check out Chinese language code hosting sites, like

https://code.csdn.net/explore/projects?tag_name=python

Of course, I'm pretty sure that's not going to convince you of anything.