I'm pretty sure (although still not 100%

) that I've figured this out now...
The way I see it, the only cars being delivered in January are the 3 identical launch cars and the 2 additional cars that every dealer is getting.
Most, if not all, dealers will have sold their 2 additional cars to customers that ordered before the end of November.
Outside of these 5 per dealer the earliest build dates are Week 3 for delivery in February.