The reasons this happens id because the Chinese Communist Party are a set of cunts.
That said, the British Home Office is almost more obnoxious in its treatment of Non-EU citizens or Brits with non-EU/Brit spouse/partners.EU
I think if you apply for a China Visa in the UK in a British Citizen passport; they are now all granting 2 year multi entry (whether or not you have ever had China visa at all before).
Presumably in HK the system is still to grant a single / double and then a multi-entry visa later on (1 or 3 years depending upon whether HKPR).
Presumably you not of (full or some) Chinese blood to be a Chinese Citizen of the HKSAR through birth in Hong Kong?
Sh*t, I have still got BNO passport. I am dead meat!
So finally went today to pickup, they granted me a double entry. Next time I'll definitely try my luck for a 6 months multiple as someone said here, every person in the counter sets their own rule lol true that!!
But my next passport renewal, I WILL try and find out how I can raise the issue about place of birth.