Well, all the UCs have increased enrollment in the last decade, with UCLA and Berkeley at ~ 30K undergrads. UCSD is just short of that at ~ 28K along with Davis and Irvine. SB is a hair over 20K. Even USC has ~ 20K undergrads, but has 25K grads(!), so total enrollment there is at ~ 45K is ~ the same as UCLA and Berk. (USC has spring admits as does Berkeley.)
The problem with SD is though it may admit a top-tier student, it has about a 15-20% matriculation rate, so it loses a lot of these top-tier students to other universities. It’s still a great STEM oriented school however.