There's certainly a difference between window glass in my house (which might stop a BB) and auto windshield glass at the compound angle specified in the FBI testing protocol (which probably won't stop a target wadcutter from a .38 snubby).
For perspective, here's an exchange from another forum:
Q: Have you tested standard wadcutters through auto glass?
A: Of course.....about 2 decades ago. It is all about the hardness of the lead and the launch velocity when confronting glass. Harder lead WC's at 744 fps went 14"; softer lead WC's at 651 fps only went 9".
In this exchange, the answer was provided by DocGKR, a reknown expert in terminal ballistics. Although it's not stated, I assume that any auto glass testing DocGKR did would follow the FBI protocol with the glass angled 45 degrees to the horizontal and 15 degrees to the side.
In any event, I wouldn't want to depend on a car windshield to protect me even from a soft lead, slow-moving wadcutter.