The other thing to consider is batching. If it's true that they do about 200 cars per batch, if only 20 people order a GT, that's 180 cars left over from the "batch." I believe someone suggested they were experimenting with smaller batches of 50 or so. But even then, that's 30 extra cars that need to be sold. Or else, you make the GT reservation holders wait.
They can't just make 1 GT at a time, in other words. So there will always need to be some extras left over from any set of orders.
The same will likely happen with Touring eventually. Pure they won't catch up on for another year, at least.