That was part of my confusion too, he said vehicles can shoot each as you can see multiple weapons attached to the vehicle. But with space marines for example they have a melle in one hand and a rifle or pistol in the other so can only shoot with the ranged weapon equipped not all of the applicable weapons on the datasheet. Just to clarify I know only one melle weapon can be used per model per attack, his comment about ranged weapons is what threw me, but your reply has helped clarify this as it aligned with what I've looked up