I would never give promise rings on a bday bc what if the relationship doesnt work out and...

This is where cultural differences come in. Those are not promise rings, those are couple rings. Korean couples get couple rings when they get together. It's not a promise towards the engagement or marriage but a symbol that to others that they're already in a relationship with someone. Simple as that

Thanks for the clarification but even in that context I personally would not give my partner a promise ring on their bday.