I particularly enjoyed the following: "That enshrines those policies in your contract.". Really ? Where does it state that in the document you signed?
Not to be outdone: "In most countries that means that if they degrade those policies (without consent) they have broken contract law."
Somewhat of a broad brush statement, which countries ? Or are you just guessing.
Don't confuse Policy (which can be unilaterally changed at the company's behest) with Conditions of Service (or in other words the terms of your employment)
I would suggest to you that the only country that matters is the one that has juristiction over your contract. Do you know which country that is? If you are based in Australia or Canada then I am reasonably confident it is those same authorities. If you are based elsewhere then I think you are on shaky ground if you think you are subject to a juristiction other than HKG law
Adam if your COS isnt to your pleasing then who is to blame?
You signed it.