Dealer prep is for removing coatings and coverings from the vehicle that were placed on it at the factory to protect it for shipping, and for preparing it for pickup by the customer. It is not there to fix the factory's quality problems.
The idea that quality is to be applied to a product at the end of the delivery chain is 1970's thinking. No world class company does that today, and especially not the auto manufacturers. It is very well understood that the earlier in a manufacturing process quality issues can be corrected the lower the costs of that process will be. Why? Because more and more value is added to the product during the process so any rework that is required will cost more the later the correction occurs. There really isn't any debate about these concepts now, just Google up the Toyota production system (Toyota was the first auto company to implement many of these practices), LEAN manufacturing and 6 sigma.
So if it really is still the practice in the RV industry for dealers to do the rework for the manufacturers, then the RV industry is ripe for disruption. This inefficiency creates a rare opportunity for a new entrant to come into the market with a higher quality and lower cost product. Its happened plenty of times in other industries, we've all seen the results in the communities that are hit hard when it does. Time for the RV manufacturers and dealers to wake up and manage the change before someone else does it for them. And none of this is the workers fault btw, the "friday afternoon car" scenario notwithstanding. Its a management change problem. just my $0.02.
https://www.youtube.com/watch?v=uTmfwklFM-M