Possibly they are making all 5,600 copies prior to release to get all pre-orders out simultaneously...that would make sense and could account for the extra time needed for the release of P3.
That would be a very bad idea, IMHO. I don't know how long they have been taking pre-orders, but I would be very surprised if even 75% of those who signed up will actually purchase phase 3 when it is finally ready for release. It's very easy to
say you will purchase a copy when it comes out and quite another to actually shell out $50 when it comes time to it--especially with the economy teetering on the edge and what not. Add to that all the other reasons why someone might change his or her mind--lost interest (unlikely, I know), lost job, lost girlfriend, found girlfriend,

moved, etc. 1,400 copies of OFF lying around unused at $50 a pop would cost the devs almost $70,000

in money they could otherwise pour into phase 4!
IMO, a better practice would be to run off maybe 10% (560 copies) in order to get an idea how many people who pre-ordered OFF will actually purchase phase 3 when it come out. The OFF people can then readjust how many copies to run off based upon these early results without having to take a financial bath if too many people renege on their purchases. In fact, they should do a test run of only 10-20 disks just to make sure that the burning/imaging process doesn't have any bugs.
Of course, I'm sure that the OFF people have thought about these issues and have already figured out how they wish to handle them.