Someone will probably have the latest scoop on this, but as I remember reading the rental insurance fine print, a person's biggest financial exposure in case of an accident is that if the vehicle is out of service for repairs for more than say 2 weeks (do not know what the real number is), then they have to start paying the daily rental charge while the vehicle is in the shop to make the rental company whole for their lost revenue.
But I am sure every rental company had their own layers draw up their contracts, and so each will be just slightly different.
I always found it curious that AAA recommends I NOT buy additional insurance if I rent a car, and they partner with Hertz, and the one time I rented from Hertz via AAA, they still tried to sell the additional insurance to me. It must be a real money maker for the rental companies.