There are many Filipinos, South Asians and Chinese fluent English speakers in HK hoping to get the high paid teaching jobs of whites and overseas born Chinese from western English speaking countries.
HK families mainly want an affordable and hard working helper. Children picking up English is not the most important reason. Most can also send their children to english teaching centres or private tuition by westerners. It is more important factor to the Mainland Chinese. They have English skills, most Mainland Chinese don't have. They would be similar to western expats in China, foreigners must have skills not possessed by most Mailand Chinese before their China work visas are approved.
Agree with most rich Mainland and HK parents want western English teachers to teach their children English, not wanting non westerners' English.
The amount of income and policy is highly depending on the relations between China and the Philippines. They can suddenly change. HK and Macau had the minimum wage rule of FDH and more open FDH recruit policy no matter the relations between the two countries.