The dam near Sacremento that got improvements in the last 8 years is a different dam than the Oroville Dam.
The spillways have never been used. They could possibly have done a better job of building them but 50 years have passed since then and they have never been tested until just now. The geology of the area is quite durable.
I go to Table Mountain every spring, which overlooks the city of Oroville. That is immediately to the north and west of the dam. That rock is as unforgiving as any rock if you happen to fall down on it. The erosion near the spillways is quite similar to the erosion around the edges of Table Mountain.
It is some hard a** rock. You can almost see where it flowed when it was molten. It is also somewhat monolithic. There is a huge expanse of flat mountaintop they is unbroken for miles, all lava rock.
I actually was in the evacuation area south of Oroville as everyone was leaving. I was not the least bit afraid. Like I said, congratulations to the engineers who designed and built it. They were the same generation that put men on the moon. If we had to build it now it would never happen because safe spaces.