It is interesting to see the variations - most likely due to different workers assigned to that station. Everyone tends to get into some form of rhythm or pattern when they do those sorts of jobs.
"Everyone tends to get into some form of rhythm or pattern when they do those sorts of jobs." mainly due to boredom or bad attitude and I can speak from first hand experience, regarding boredom.
Once had a college job on a small 'assembly' line packaging foods like iced tea, etc. One job was putting the plastic scoops in the cans and I know some of you might have gotten 2 scoops (or ....even 3!
) in your can once in awhile. Labels might have been upside down too.
I don't have to guess how/why some of the things got done they way they did on our cars.