This sudden decision is made after the exchange denied they were closing down on September 10th, telling trustnodes at the time. That appears to have changed. The reason remains unclear at this stage. The September 4th notice concerns ICOs as far as we are aware. There are rumors of a new notice which suggests China is to ban crypto exchanges. However, some clarification appears to be developing which suggests they will only require a more strict licensing regime, rather than closing them down. But, in the transition process they might have to close. A step which BTCC has now taken.