They are now defective tires and should be replaced under warranty. Heck, maybe the dealer even knew they were defective? Do not let the dealer or Goodyear get away with not replacing them for free. BTW that the dealer even suggested putting the defective tires on the back tells me they may be shady...
I suggest you look up the definition of "Defect".
A belt separation in a condition that has a cause. The cause may be a defect such as some contamination was built into the tire between the belts or the wrong rubber compound was used on a batch of tires, as I discovered when inspecting tires back in 2000. As I pointed out in THIS post there are also external usage factors that can contribute to the initiation of a belt separation.
If you worked in a coal mine and after 30 years were diagnosed with "Black Lung" would that simply mean your body was defective which would make the condition your parent's fault?
If you had a sidewall flex failure due to running with only 20% of the air pressure required to support the load is that an indication of the tire being "Defective". You can learn more about this condition by reviewing THIS post in 2011 on Sidewall "Blowouts".
Simply claiming a tire is "defective" is the go-to excuse used by many that have no working knowledge of or don't want to spend the time investigation the "Why" tires develop various conditions.
If you have a tire failure and even if you don't know why it failed. Even after reviewing the posts on this blog that identify various reasons for a tire to fail, I still suggest you file a complaint with NHTSA. Please however just describe the condition of the tire and be sure to include the vehicle VIN and the full tire DOT serial.