They end up with lower graduation rates because they start out at a severe disadvantage. As you know, most Asians and many/most whites in the UC system have very supportive families who have always made sure their kids had the resources to succeed.
It doesn’t hurt them, but it won’t guarantee that they will succeed in schools as well as the Asian and white populations do, either.
IMO, most of the “exceptional” students will succeed anyway. The quota system is there to give others a fighting chance.
And note that the black student population has also gone down since they eliminated AA at the universities. Asians, OTOH, seem to have fared about the same before and after Prop 209. But we also have to look at the population increases of various groups, and Hispanics have grown in number far faster than any of the other groups which might explain their increasing numbers. Whites, as a percentage of the population, have been decreasing (as have blacks, IIRC). Asians have been increasing, so the fact that their percentages at the universities are the same might mean there’s a slight decline as a percentage of the population. Not sure about any of that, though.