Um...things change?
I do not know if this was the case, but when you are developing something the tolerances are going to be smaller than when you mass produce it. So maybe Ford said "It would cost to much to produce that part that accurately" (Something Porsche does and turns the cost over to the consumer) so they change some things so it can be way off but still function fine. But all those mismatched factory parts add up and start killing the output...
Just speculating...don't take me too seriously.
