I totally feel for you and your frustration. I have two kids who went through the process. Both were high stats (almost perfect SAT score, all 5’s on AP tests), same high school, same ECs except the younger one had more passion projects related to major. One applied 2015 and the other applied 2020 and what a world of difference those 5 years made. First one was accepted everywhere except Harvard and Princeton and enrolled at Stanford. She was admitted to all the 5 UC’s she applied to. The second one didn’t even bother applying to Ivy’s or T20 privates, only OOS STEM flagships and 6 UCs. He had a 40% hit rate in terms of acceptance (which I was so thankful for given all the horror stories out there) and enrolled at UIUC. My personal theory is that given the explosion of apps each college is receiving the last few years, high stats no longer matter as much as they used to, especially at test blind schools like the UCs. I also believe there is grade inflation at many high schools and the number of 3.9 - 4.0 kids has steadily increased and many are in for a rude awakening when they receive their first B in college their very first semester or quarter. When so many kids with similar high stats are applying to impacted majors, AOs will look to essays and PIQs to determine “fit” and who best fit institutional goals and priorities which do not always translate to applicants with the highest stats. For example, they may have a goal of enrolling at least 10% of the class with first-gen students, so a 3.9 first-gen student may be admitted vs. a 4.0 non first-gen student may be waitlisted for the same major at the same college. All part of holistic admissions.
I now work with low-income, first-gen high school students through a 1:1 mentoring program. The program provides excellent training for college mentors like me and my advice to all UC applicants is to really spend a lot of time on your PIQs, starting the summer before senior year. Get feedback and iterate. This is the only way you can stand out since stats and activities (usually accomplished musician/athlete/club president) are so common these days. You need to be memorable and the best way is to choose the PIQ’s that showcase you the best and tell complementary stories about you. Also important is to strive for a balance of story-telling and reflection. The best PIQs are well-balanced between telling what happened and reflecting upon the event…what did you learn about yourself, the world and how did it shape or change you, your outlook and what you want to do in your future. If the essays are all story-telling or all reflection, they don’t showcase you as well as ones that are well balanced between story and reflection. Obviously, not going to help you or your student now, but if you have younger ones, you have more tools, knowledge and experience to help them. Not implying that your student did not have stellar PIQs, just advice to future students who hang out at CC forums.