Perhaps you could arrive at the assumption that the wording of TIMATIC means that's it not for the airline to assess the appropriateness of the booked exit port, only that they appear to have a ticket booked to a third country within the required timescales, and that the exit port is a potential item of debate at China border control, which could potentially be fixed at the China border by most internet savvy travellers with the purchase of another ticket (or maybe escorted to a ticket desk airside or landside to remedy their onward travel).