It is likely that once one very large hailstone caused cracks, follow-up strikes that would have bounced off an intact panel created further cracks in the alrea

It is likely that once one very large hailstone caused cracks, follow-up strikes that would have bounced off an intact panel created further cracks in the already damaged and now weaker panel. So the still intact panels are probably not significantly stronger, they were just statistically fortunate in that they didn't receive an impact that started a progression of further damage.