or do they just put a longer club shaft in the head I'm fitted for?
Why an inch over..? If the fitter says you need longer shafts, fine, but to request a longer shaft baffles me. Care to shed a bit more light on your question..?
PING, or any other company, will only do what you tell them to do. If you told them you want an inch over and black color code, they won't actually make it purple because the extra length makes it play more upright.
Yeah you won't really gain much speed going longer, adding an inch just made them heavier.