It makes sense to me.
As a Sergeant, I want my subordinates to feel safe opening a complaint against misconduct by ANY person regardless of rank without worrying about any harm coming their way.
This is the same with Staff Complaints being anonymous so that the person complaining doesn't feel as if they are placing a target on their forehead by speaking out.
Action Requests are more of a matter between two people of generally equal power-standing, kind of like a civil dispute, so it makes no difference in most cases.