It's possible that China censors info about Tiananmen square because so much of what was published came from Western news orgs - and the West has form for using the "news" to attack other nations. Another example might be the supposed "genocide" of the Uyghur people - the MSM pushed the genocide narrative hard, while radicalising, funding and arming Uyghur Islamic extremists, so they could control the narrative. And of course, it largely worked.