I am from the US and wondering if the 24 hour free transit apply to cruise ships?

The ship will be arriving on 10/14/18 for a 15 hour visit to Tianjin & Beijing. This is a 60 day trip from L.A. and returning to L.A. We will be visiting 15 foreign ports as well as some U S ports. We arrive in Tianjin port from Japan on 10/14/18 for a 15 hour stay. Then we leave for So. Korea. A few days later we visit Shanghai for 15 hours and then sail for Okinawa. On 10/23 we visit Hong Kong, again for 15 hours. Then we head for Vietnam.
My question is will I need entry permit for this short say in Main land China (Beijing)? After extensive reading regarding this subject, It would seem that the free rules would apply to me, but the ship is requiring single visit China visa before boarding. Can any knowledgeable person enlighten me as to the reason why the cruise line is requiring this. I have not been able to get a decent answer from the representative at the cruise line as to why, except to say that to qualify for this visa the ship must leave from Shanghai and end in Shanghai. But I have not read anything as to this requirement. Besides it doesn't make any sense since this requirement would defeat China's purpose in getting more transient to visit these places..