Doesn't make sense
Well right now that is what the NTSB saying. Oversized holes and elongated holes or double holes. Apparently the overlap joint has been loose at least since the last repaint as the paint (Blue in this case) had seeped between the lap joint.
So, in sum, wrong sized holes at the manufacturing level where thousands of fasteners are installed a day seems highly improbable where not only are the installers involved, but also the Q.C. guys. It doesn’t make sense. Boeing has had a number of controversies but the very basics of fastening shouldn’t be one of them
This appears to be the direction that NTSB will be looking. Something wrong in the manufacture of the lap joint. As you suspect Data Guy that should be basic operation. Something is not passing the smell test here.
VFD