Windshield spontaneous crack

My windshield one cold day out of the blue cracked. From the bottom up about 5 inches and then across the window. I claimed it was defective glass that the dealer should replace under warranty. But they used this "ball point pen" test. They run a ball point pen along the crack and if they feel any chips then they say that the window was damaged by an object hitting the window.

My claim is this is not correct. That the act of the window splitting is dynamically a "violent" event and it could easily pop a sliver of glass off in the process. Which is what they found, a minute sliver on the crack barely noticeable with the naked eye. I claim that an object striking the window to start this cracking process would not simply remove a sliver from the window but that it would have to induce the star pattern that we often see at the start of the crack.

So I guess I have three questions...
1) Could an object striking the window just remove a slight sliver with no additional cracks that we see in the typical star pattern?
2) If this is possible would that weaken the glass to the point that a crack would suddenly occur on a cold day without any other "force" applied to the window to start the cracking event?
3) Could the cracking event, which initially occurred with a couple of load pops, have caused the sliver of glass to chip off? (I was driving very slowly in a major snowstorm with the road completely covered in snow and no cars in sight. So I know the audible pop was the event of the window cracking and not the event of an object hitting the window.)

I know this question probably seems ridiculous but I am an engineer so my inquisitive mind is getting the best of me.

I appreciate your time and any consideration you give this question.