Duster rocker to 1/4 panel seam

I have noticed that the '74 and later Dusters did not have this seam finished. I am wondering if it was a particular plant that did this. Just curious. I'm sure it saved some money and I'm sure my observation is not the norm throughout the entire production. My '70 Hamtramck Duster has the seam finished but my '74 St Louis Duster has it unfinished. Also noticed the later tail panels were not entirely blended in/finished especially near the bumper top.