I don't think it is a line. I think it is more of a series of sets, where a set is defined by region, another by color, another by trim. When the correct intersection of the sets occurs such that Tesla can deliver the single largest amount with the highest rate of success and profit, then you will get your car. So if you put yourself in the correct set, then you will get your car earlier. My theory on the model 3 initial ramp is they had so many options, that they had to many sets, and the intersections were not large enough. Later they reduced that, for instance premium package was included, RWD was removed, etc. With the Model Y, they started with many fewer sets. So now, only the computer knows the right set, and which set will be produced first.