I know nothing about this sort of stuff, but if this were applied to cars, would there be an increased risk of temporarily blinding other drivers on a sunny day?
Flat scattering surfaces are never blinding. The problem is with specular reflections off of shiny surfaces. Even though a shiny surface may only reflect a small fraction of incident light, it's all pointing in one direction which can dazzle observers.
For its intended application, reflecting 98% instead of 90% means absorbing 5 times less heat when under Sun light.
That is a very large difference. A white paint with only 90% reflectance might cause negligible cooling, while one with 98% reflectance may cool a painted object to have a temperature less by more than 6 Celsius degrees in comparison with the air temperature.
The cooling depends on the ratio between how much solar light is absorbed and how much far infrared light is emitted.
So a cooling paint must be very white over the near infrared, visible and ultraviolet spectrum, but it must be black for the far infrared light which is emitted by the bodies at ambient temperature.