What makes you so sure the cars with "workmanship" issues are are as safe as the ones that were sent for safety testing?To me the fact that Tesla makes by far the safest cars on the road is so much more important than "workmanship" as you understand it that it's hard to express.
Tesla gets to hand select which cars are sent for testing, and I highly doubt they select cars with imperfections for testing. If Tesla can't consistently assemble surface components properly, why do you think they are more careful with structural components.