Oh, this is an interesting one.
HR always gets the blame for people getting promotions, and that really is not the case. HRs role is to ensure fairness to all employees. So in this case, when the supervisor said, “I need to go to HR, ’cause they’re the ones that decide”, they really don’t decide. They evaluate the situation to make sure that if this increase and promotion is warranted and justified and doesn’t cause an inequity amongst the company.
Then the HR department would approve it, but it’s not HRs decision. HR is just following policies that have been established by the company. And so again, the supervisor probably didn’t have the training to understand the process and use some terms that they probably shouldn’t have to the employee, which would make the bad guys look like HR, when it really wasn’t HR. It’s the company itself.