Being employed on a base by CX can in no way confer employment rights in HK, to support a work visa for ex CX based pilots would require lying on the company’s supporting documentation that there were no available suitable candidates locally. That would be a criminal offence. Eventually the company gave a job to every suitable applicant ex KA which meant that supporting visa applications is now legal.
The based pilots now have a good deal in that they can come back in their previous rank and pay.
The KA pilots were merely making sure that immigration knew they were qualified and available, they were looking after their own interests and why shouldn’t they?