This I have found to be true at some dealers, typically the ones that are trying to rip you off. Mega dealers are out to move a lot of cars and typically you can get a better deals there. Smaller shops tends to apply all the tricks, pin stripes, window tint, vin etching, market adjustment, etc.. These folks want to start price negotiation at the "bump sticker" price with the add ons, even when the vehicle you are viewing doesn't have any of those items applied. I have gotten better deals from other dealers that are not on the Costco list for KIA's and scored even better at other brands, without it.
For the First Editions, I seriously doubt there will be a Costco incentive for them. If the cars are slow selling or they want to improve sales, the manufacturer will offer more incentives and you will find other entities, Costo, etc., offering incentives as well. We will have to wait until the car is in the market to know for sure how this will pan out. Plus, how the chip shortage will affect this as well.