The problem is that position, while a valid control, may confuse people because they can't grasp how to apply it. It actually defines a cylindrical tolerance shell AT the diameter. But the simplest way to interpret it is is as a cylinder on the center with a diameter of the true position callout. This makes people think "round." But true position can be applied to any shape.
If it were me, I would have either gone from the center of the hex to the midpoint of the side OR the width across the flats and controlled it with symmetry. Then marked it 3X to cover the other flats (or 6X if I chose the radius method).
To your shop floor guys - ask them this ..... If the control only controls the tangent points of the flats, then what, exactly, controls the corners?
(In other words, they are wrong. The entire shape is controlled. But again, the callout is just implemented poorly).