Just to point out build slots are either for petrol or diesel.. not 4cyl/6cyl diesel/petrol. You can just pick a bulid slot for a 320d msport and change it to a 330d msport.. or you certainly could on the E9* cars.. has it changed for the F3* cars.
So i dont know where the information is coming from. Though once you pick one of they slots, and amend the spec it can push it back a few weeks.
It usually takes 3-4 from being bulit to dealers.