Because China Gov owns around 200,000 btc and this is a lot. More than US government. By reasoning, their voice is bigger compared to US government in cryptocurrency.
Should we take china words seriously? No. Because they been trying to ban since year 2013. Then they un-ban and then they ban again. History repeats.
Is that serious any source for the 200k btc owned by China. Regardless of their asset. Their trying to stir up the market but what happened they never succeeded once they launch their own. Im not sure even their own people would be buying those or using it. Most Chinese believe in the bitcoin and crypto era rather than their own plan coin.