Impact rating is a test result, not a promise
An impact classification describes performance in a defined test. It is useful information, but it is not a promise that a roof will escape every hailstorm. Wind resistance, color and impact resistance also are not interchangeable labels.
A Class 4 product may be worth discussing when choosing a replacement. Any insurance discount depends on the insurer’s current requirements and the installed system, rather than the class number alone. The cost and suitability of the product need to make sense for the roof even without assuming a discount.