As I recall, all wings were/are manufactured by Mitsubishi Heavy Industries
Correct- but the area mentioned is where the wings are attached during assembly to the 'wing box ' and done at the factory during final assembly.
That area has always been a difficult to join area, and is essentially the location of previous 787 wing problems during structural tests- and if I understand just what parts are involved, they were a major issue in the first few 787 built. And the AD numbers of $80 85 dollars to fix/correct is IMHO a bit phony..