I checked one of the partscar and one of the wagons. The red and green primer can have been absorbed by the seam sealer. If they had the seam sealer everywhere the primer could not get in everywhere. That's my thought. Not sure I'm right though!
I certainly am not an expert on these cars, especially the earlier cars like yours. All you can really do is study your car during disassembly and study as many other cars like yours as you can. I'm not sure if they seam sealed all locations while the car was still bare metal but I think they may have done some areas before priming or dipping.