CX used to hire crew with diversity because many years (like 20 or 30 years) ago, very few local Hong Kong spoke fluent English, plus people from some regional areas do not actually speak English at all. Therefore, it was necessary and it's a policy to have the "local" crew accordingly, like Thai crew for flights to BKK and Japanese speaking crew for HND and NRT. Therefore, you met SP (who is probably in her 40s) should be hired 20 years ago. The regulation and policy still exists. However, with the not so attractive salary and no more housing allowance, potential candidates would not prefer to come and work in HK where rent is high. It is not mandatory and I have not heard of hiring from China. There is also tax issue. It is serious crime and fraud to work in HK without visa.