How did Guangzhou and Shenzhen become "Northern Guangzhou and Shenzhen"?

Beijing is the north gate and Guangzhou is the south gate, and their positioning in China is the same. Why is Guangzhou and Shenzhen ranked among the North, Guangzhou and Shenzhen? Because Guangzhou is the national trade center, the first trade capital of China and the historical capital of the world. Shenzhen is the second financial center in China, the first service area of Shenzhen Stock Exchange, the second largest financial institution in China and the first special zone in China. Why can't these two cities rank in the north, Guangzhou and Shenzhen? Beijing in the north, Shanghai in the middle and Guangzhou and Shenzhen in the south can all be strong.