You are quite right, the Chinese stock market is relatively small compared to the size of the economy, which is why it’s wild swings and their cack handed managment of it has done limited damage. The point is that just having enormous powers of executive action is no guarantee that action is going to be effective or even competently executed. Their mismanagement of the markets was just a case in point.
Eventually the Chinese government is going to face a real, full bore economic crisis. Hopefully that’s a long way off and they will learn many lessons before then.