You are right, I have searched for this. Still, I can not get any concrete information from the Chinese website or any reliable sources we can hold onto to be genuine but however, but we all know the Chinese government is very strategic when it comes to trade deals with the US government. I doubt they would be quick to sell off their treasury bond with the US, as it would be too early for them to do so, looking at the fact that they are having trade wars with the US government. Although they have retaliated, which shook the world economy and that of the US, maybe we should call it "a test on the microphone," and a warning signal to the US. They would hold onto their Bond for future retaliation if anything funny happens again.
I also took the time to verify this news and like you, I didn't even see any major and credible news sites mentioning this. Only a handful of tabloids reported on this, making the information unreliable.
It's true that China's holdings of US Treasury bonds have been on a downward trend in recent years, but the reason behind that is that they want to diversify their reserves. The trade war is still under China's control, they do not need to rush to use key cards to respond, and selling US treasury too quickly is not beneficial to them. They are wise enough not to act hastily. So I confirm this is fake news.