Gorilla Glass" was also supposed to have survived the "frozen turkey test" (frozen turkey fired/catapulted into a sheet of given product).
I'm no materials expert but I would question how thick said sheet of glass was. 6 inch piece of glass will obviously have much more stopping power than the 1cm that is in a phone screen.
The other thing that I would just like to throw out there is that glass is very finicky. I have dropped smart-phones and been certain that I broke the screen, only to pick them up and have the screen be intact, I've also had the opposite happen.
Is Gorilla Glass stronger? According to the manufacturers and to some of the tests that we've seen, yes. Is it un-breakable, NO! I think a lot of the screen breaks that have occurred are very subjective and given how glass behaves under certain conditions it is hard to say that it's Gorilla glasses fault.