I suspect they're offering the coaches first, because the models are more or less available now. That will whet the appetite of the collectors, and generate the revenue that might be necessary to tool the couple of uniquely AFT cars (which judging by the photos will be lightly modified baggage cars and something from the MT circus train toolbox, not necessarily all new custom tooling).
Given that the target market is going to be collectors, I'll stand by my remark that it's absurd to expect a tee-totally perfectly prototypical set. Considering that decent passenger cars go for $30+ these days, the $49.95 per unit doesn't amount to a custom run car... It's retail plus attractive paint scheme, plus the "Elvis Plate" factor (Collectible).
Lee