I see this article says that chemically strengthened glass can be cut, and while it becomes weakened in the vicinity of the cut, it does not shatter as a result. The Wikipedia article does not explain in any detail why this is so, but it suggests that there is less tensile stress than in tempered glass. Perhaps this is because the latter needs the internal tension to create the surface compression, while in chemically toughened glass, the compression is generated within the surface layer?

I have seen it said about Supafest drinking glasses that they do shatter into tiny pieces when they do break, though I do not know whether the source was reliable. If this is the case, then it suggests there is some difference between the Supafest and Corning / Gorilla Glass processes.

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.