Once the water starts churing in that hole where already damaged. How long would it take for it to eat it’s way back towards the lake? If so, the hole would widen so fast it would be (in my opinion) nearly as bad as the dam bursting in the end. Water would continue to chew it’s way though as it washed away more and more dirt and concerete spillway.
This is a terrible event just waiting to happen.
Keep in mind that the Oroville Dam is an earthen dam!