I think your point is essentially correct. However I think most of us believe there is a slight advantage to front porting. The cabinet inverts the phase of the rear driver radiation, so cone and port are in phase. So by having the port in the vicinity of the driver is a little more synergistic than a rear port.
Rear porting is done if the port diameter is inadequate. Manufacturers are know to do this to hide the chuffing.
Often in a bookshelf there is no room on the front for the port.
I try and front port where possible and I do believe it carries a small advantage. So doing it this way gives the best phase coherence.