It's not unlikely that they only went with Gorilla glass for the screen-side of the device to cut costs, though I know the article says otherwise, so maybe not.

It's not unlikely that they only went with Gorilla glass for the screen-side of the device to cut costs, though I know the article says otherwise, so maybe not. They could've also mounted it in a way other than what was designed (i.e. put it under tensile stress). As for Corning, in fairness to them they were instrumental in the development of this type of glass and own a fair few patents, so it's not just marketing. They developed it originally in the 60s, though I imagine a lot has changed since then.