I don't think that they were upset "they couldn't screw you", probably just trying to get you in and out with your order. No reason to try and sell you anything if you are ordering. I would bet that they treat you great when the car comes in and at delivery.
You have it all figured out. See I saw it opposite, guys like you would come in bragging about how much they knew and threw around terms like invoice/holdback. I don't know why everyong seems to think that they are entitled to holdback. BTW, most dealers don't make the money on new cars, as "they are aware of the age of the internet". Most of the profit in sales is generated from the used department.
awesome...you hit it right on the head.