From where I sit it sounds like a way for the head of the department to deflect questions from new people onto tenured people. I guess it's a good idea in theory, but if it isn't required, I wouldn't be on board with it at all. It sets up a confusing chain of command, like you said. I would think anyone tenured would be willing to answer general questions or refer you to the department head. Maybe don't bring it up and just leave it alone?
Do you really need one? Sometimes the best thing to do is nothing.