Busan via Huangzhou and Beijing to Copenhagen

We are Swedish and on a visit in Busan, Korea. Our ticket back to Copenhagen by Air China involves two stops inside China, Hangzhou and Beijing. According to your information this should be Ok with a 24-Hour TWOV (applied for in Hangzhou). Is this correct?
Air China call center say it is not possible with a domestic flight with the 24-Hour TWOV. But yet other sources say it is OK, including a person handling transit or temporary VISA excemption at Beijing who I asked ion the way here.
So what is correct?