Why are so many Hong Kong people born in YVB born in Guangdong?

Hong Kong itself is a part of Guangdong, and most Hong Kong people are descendants of Cantonese. Except for a few indigenous people. Most Hong Kong people fled before and after the founding of the People's Republic of China. Among them, the period of land reform was the most. Guangdong accounts for the vast majority.

This is also the reason why people who have the ability to emigrate have gone abroad before the reunification. Because I'm afraid there will be another scene of escape.

But then I saw that Hong Kong was basically prosperous and stable. Not to mention the economic downturn of more than half, many immigrants have returned to Hong Kong.

So, what is strange about being born in Guangdong?