Just to be more specific, HR is an agent of your company. Their job is to make every interaction resolve in favor of the company. Often, this is a good thing for you, because when things are running smoothly, a lot of the stuff that is good for the employees is good for the company.
The important part to always remember is that when there is a clear conflict, a situation where something that is good for you is bad for the company and vice versa, their job is to make you lose. Their job is to be the negotiator that resolves the situation maximally in the favor of the company and against your interests. In those situations, it is important to remember that "your boss, hr and you" is not two parties and a neutral intermediary, it's two parties, one of which has two representatives. Bring either an union rep or a lawyer.
I don't think you mean "legally bound" here - there is no legal obligation for HR to operate with anyone's best interest in mind, corporate person or organic person.
Just to be more specific, HR is an agent of your company. Their job is to make every interaction resolve in favor of the company. Often, this is a good thing for you, because when things are running smoothly, a lot of the stuff that is good for the employees is good for the company.
The important part to always remember is that when there is a clear conflict, a situation where something that is good for you is bad for the company and vice versa, their job is to make you lose. Their job is to be the negotiator that resolves the situation maximally in the favor of the company and against your interests. In those situations, it is important to remember that "your boss, hr and you" is not two parties and a neutral intermediary, it's two parties, one of which has two representatives. Bring either an union rep or a lawyer.