Tire Sidewall problems of the 2005 Ford Focus

Goodyear eagle gt tire shows signs of tread separation around perimeter of tire where sidewall meets tread.

I recently had a tire failure. I am not sure what to call it as the entire middle section of rubber came completely off. There was only a small amount (if any) sidewall left (I have photos). I took it to a goodyear dealer who replaced it at a "prorated" rate although my understanding of the warranty was that it would be completely covered. I had it replaced and paid the $80. 00. I also contacted goodyear to make sure this was their policy and that my transaction was handled correctly, I included a photo with my correspondence. They informed me that it was their policy and the dealer had contacted them about my incident. They also assured me that a tire should not do that and they are sorry about it. I am feeling that this is a very dangerous possibility, if it had been a front tire I would not have survived the incident as I would have lost total control (goodyear tire).