Cruise which calls in to Shanghai for 16 hours

We are UK citizens with UK passports and are taking a cruise from Tokyo to Hong Kong in October 2016. This includes a stop of 16 hours in Shanghai. The cruise company are insisting that we will need entry permits for our day in Shanghai and say that they will not allow us to embark on the cruise without them. However, our reading of the new Visa Waiver regulations suggests that, because we are UK passport holders and will be in Shanghai International Cruise Terminal for less than 72 hours before travelling on to Okinawa, we will not need to have an entry permit. Would be very grateful for a clarification.