Dear spectacularly refined chap,
No the 12 month build isn't blown out of the water, perhaps it takes 5 years to decide you need a fab, budget for it, design it, architect the structure, clear the site, get the permits, order the machinery, clear the site, train the workers, build the facility, install the machinery, start production.
But its is clear that the "build the building to start production" part can be done in 1 year, they did it. You don't know if for instance they already have all the stepper machines and what not on order for Phase 2 of Fab 5. And since the second part of Fab 5 is a duplicate of the first half and the site is already cleared it does not seem like there is any activity that is externally visible that would prevent them from starting construction tomorrow and being ready to sell flash a year later.
Given they have talked about starting construction next year one assumes they must have things like steppers and the like lined up for potential delivery. In which case they will start building a duplicate of the building they just build and a year later it will be online making parts using equipment ordered 1 year before the started on the building.
Its important to distinguish between "it takes X years to build" and "it takes X years to plan for and build the first one and Y < X years to build a new one after the first one works"