It's due to the thickness of the compressed layer at the surface. It's often thinner (but more intense therefore harder) in Gorilla glass, so I suppose there is

It's due to the thickness of the compressed layer at the surface. It's often thinner (but more intense therefore harder) in Gorilla glass, so I suppose there isn't enough tension in the interior to make it shatter. There's always a corresponding tension in the interior, the sum of forces in each direction are balanced. But if the outer compressed region is thin, you won't need as much internal tension.