A script that never answers
Thousands of commercial themes still load jQuery from Google Hosted Libraries. That one tag is render blocking, so the browser waits for it before painting anything at all. The visitor sees a white page for a few seconds and leaves. Your analytics never record the visit, because analytics didn't load either. You lose the visit, and you leave the impression that your company doesn't work in China.
GreatFire's last conclusive test of ajax.googleapis.com from mainland China failed, and it classes the host as blocked.