I haven't read all the thread on this topic, but I read a sufficient amount to know the issue.
Here is my take:
I've taught R1 universities for several years so I have a first hand experience on some of the issues.
I've also spoken with Professors in Asian countries and we discussed the differences in education system between Asian countries and the U.S.
Generally speaking, Asian students spend a significant more amount of time than the U.S. students in studying and getting ready for colleges.
It is also true, Asian students are good at test taking. This is the key that is missing in this issue. Because Asian students spend a lot of time memorizing facts and practicing test taking, they score extremely well (as a general rule) in standardized tests.
But UC systems and other R1 universities are NOT built on brute memorization and test taking skills. Yes, test taking is a skill. What UC systems and R1 universities are looking for are not only students who can do well academically, but ones who can think independently and "outside the box", if you will. Ones who can think independently and do independent research and can be the future leaders.
In my experience as an educator, this is where Asian students do not out perform other ethnic groups. They are no better than any other ethnic groups when it comes to independent thinking. In fact, one can argue that Asian students are worse off then other ethnic groups in independent thinking. Why? Because they are taught to obey. Obey their parents, elders, teachers, etc. Basically, Asian students are taught to "not to rock the boat", if you will.
While the policy changes to the UC system may de facto disadvantage Asians, I believe it is not intended to single out Asians. I think the policy makers wanted to ensure that the policy changes attract more independent thinkers, not just students who can take tests well, but those who (while not good at test taking) are good at thinking out-side the box.
I have empirical data to support my position in that one of the professors at a top universities in Asian Country agreed with my assessment. He was disheartened at how terrible some of their top high school recruits fail miserably when it comes to independent research.
So, unless proven otherwise, I support the changes instituted by the UC system. Test scores and academic achievements are not and should not be the end all measuring stick for admission.
A crude analogy to golf would be if you are picking someone for your four-some for a best ball (not scramble). You see a guy hitting his driver really well at the range and you pick him as one of your foursome. Turns out, that's all he is good at. Hitting the driver. He has a terrible short game and putting.
Just my 2 cents.