I hope the glass is better on the X. I don't think the second rock that cracked the windshield on the S would have even pitted the glass on my BMW.
The issue isn't the glass material. A lot of things come into play - the specific shape of the rock and the slope of the windshield are two major ones. A rock that has a sharp, pointed edge that lands point-down will damage nearly any production windshield in the US. It's why there are some rocks that will damage even the latest, strongest gorilla glass if you drop your phone on them, yet many drops onto driveways with flatter stone will survive.