the only thing I can think of was that there were multiple parts suppliers feeding rods into the MOPAR assembly line. Some went back to strip the copper off, while others just pushed them out as is since it has no effect on their performance other than to boggle the minds of owners 50yrs later.
I mean think about it, the line was manned by people just like you and me, if it really didn't matter, I would be mixing them as well out of boredom