If completely assembled, how no paint on the header pins, J hooks and chrome bits they screw into that are pressed into the latch base?
I'd bet sub assemblies were used, and assembed and adjusted post paint for those sub units. Possibly some touch-up after that, and then the fabric applied before shipping the entire thing to the line for installation.
Seen many apparently unpainted screws for the side links to frame, and the chrome as noted would not be painted (or masked, as that would be even more time consuming as its a fiddly area).
I'd also guess header was off (otherwise adjusting could leave an exposed line of unpainted metal), side rails assembled, but side links and bows done off (again adjustments would possibly show bare spots on eccentric and bow #2 which I don't think Ford would have done).
And yes, it is all speculation...