Is the Shenzhen VOA available for holidaymakers?

I read above that VOA is only for emergency situations where a visa could not be organised earlier, and requires a company issued letter to make it happen. Does the Shenzhen 5 day VOA require this, or can any holidaymaker get the 5 day pass so long as they go through the process steps of the application at the port? Is the answer the same for Hainan and Zhuhai also?