When I took the checkride for my current job I joked that I wish I could have put the evaluator in the backseat of the plane I was currently flying and do the check instead of an airplane that I had never even set in the cockpit off, much less unfamiliar with the avionics, and shooting approaches that I had never used or hadn't used in nearly 20 years! That is some added pressure.
The ramifications of failing the ATP checkride after a quickie course, and the ripples it could cause on down the line of a future career are serious. It would like taking that airline guy who wants to be a military pilot, putting him through the ground school and sim for two days and then having them perform to a high set of standards for a job in that next 20 years. That would be viewed as unfair and a foolish way of evaluating potential pilots.