Are you referring to the Admissions by Discipline on the UC website?
It specifically states:
The data should be used as a general guide to selectivity and not as a predictor of a student’s chances for admission to a particular campus or major.
While freshman applicants to UC indicate a proposed primary and alternate major for each campus on their application, major choice is generally not a factor in freshman admission.
The UC’s collect data for statistical analysis and to help plan enrollment resources needed to meet the demands of the in-coming Freshman students.
Even though they may not consider an applicants major in the admission process, they are going to review the student’s PIQ’s, academic profile and EC’s to get an overall picture of the applicant’s interest and intent when listing a major so they are considering a campus fit which includes intended major.
The UC’s do not expect a HS student to specialize in a particular subject/major and know many students change their mind so L&S admits have more flexibility to switch majors than in other colleges but the overall application should present a cohesive narrative.
My advice is that applicants should always list the major that they would prefer to study.
Here is a link that explains the UC Comprehensive review. How the University of California evaluates student applications | University of California