I think re-creating the aircraft in 3D only takes perhaps a week (exterior model) and perhaps the same for the cockpit view! If all the references are good and the devs decide the cockpit represents historical accuracy!
However I believe the 6 month thing is said to be a full- flyable aircraft with what I imagine to be the most time-consuming task : To animate every single lever, button, gauge, mechanical part etc etc etc. I think that's where the working hours go
