144-hour stay in Shenzhen

I hear that Foreign tourists holding a visa for Hong Kong and Macau can enter and stay in Guangdong province for up to 6 days using a 144-hour Convenient voa. Valid entry ports are in the following cities: Guangzhou, Shenzhen, Zhuhai, Foshan, Dongguan, Zhongshan, Jiangmen, Zhaoqing, Huizhou and Shantou. I hold a US passport and live in California - so does it mean I can fly to HK, take a train to Guangzhou and able to stay there for 6-days then train back?