I take some umbrage with that, since they have had 3 years I believe. More if Woogity was doing concept works years before the game was released.
Now that the models are completed and in game, and have motions and animated poses, I'm fairly sure they could port them to CAD without to much difficulty, adjust any issues that would come up, and then start the undercutting process.
That would take, what, a few months of work for a few kits? Depends on resources and who is doing the undercutting. There are some real geniuses out there when it comes to that.
Setting up sprues would happen alongside the undercutting, so they fit fine. After that, it's just slapping it off to the production facility in house, printing loads to put on pallets and store for release day, which is not soon by their own admition.