If you had the truck and this tool, it would all make sense. The plug wire ends go down into the head too far to grip onto anything to pull (on anything but the wire anyways, don't do that!). And also the clearance is so tight that a normal spark plug wire pliers won't usually work either. The last few plugs are the worst, sometimes a careful tug on the wire will get it, but as a last resort only. OTOH they will remove from the coil quite easily by hand.
But on the plug side, there is just a little metal sheild left that this wrench will engage on to, then you can carefully "lever" the plug wire off the plugs. Even then you need to use caustion, althought the worst I've ever done is to have the plug insulator crack and remain in the boot, then the insulator can be removed fairly easily though.
Gilly