I’ll share my son’s application approach, which seems to have paid off so far with the UCs (@tamagotchi My son has the exact same results as your son, although UCSB accepted him into L&S instead of engineering, so that’s automatically out).
My son has a 4.0 UW/ 4.25ish UC, and I think 9 APs, but no state or national awards or internships, etc. While he’s taken all the major STEM-related AP classes, he chose not to take the AP classes that didn’t appeal to him, like AP English or AP Economics. He’s not in a ton of ECs, but he focuses A LOT of time on Robotics. His school’s team is pretty young and much less funded than others, so they don’t make it to the national robotics competition level. But his best PIQ was about how their robotics team got absolutely crushed at the regional competition in his junior year, but how that just inspired him to take the initiative to make changes, learn more, and be a leader. Also, instead of taking DE classes that fulfilled requirements, he took a series of CC classes that got him a certification in computer-aided design (CAD), so he could help better design his robotic’s team robot this year. He also wrote a great PIQ about being a long-time volunteer for a local food bank, but not really understanding the impact of the organization until actually seeing people line up for food during the pandemic.
I worried he would get overlooked by the UCs because he doesn’t have all the “traditional” accomplishments I thought top students would. But his full application told a story about a kid who really wants to be an engineer, is passionate about the activities he’s involved in, and focuses his time directly on those things. I truly believe that storytelling approach has worked for him, and a reason I’m thankful for the holistic review of the UCs.