The doors are different than pickup truck because of the moulding/body line at the top, which needs to blend with the side moulding/body line on panels and Suburban's. Truck doors do not have that feature.
You can see it in the link I provided. See the TOP of door. I am not an expert on these whatsoever, I am just remembering what others have said. Just google trucks and panels and you will see...or look in the gallery here.

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