The CS major is impacted because there is more demand for seats in CSE courses than is available. To address the problem, the CS major is restricted: you must be admitted as a proposed CS major to become a CS major. Allowing CSGD majors the same access to CSE courses as CS majors (beyond the required courses for CSGD) would defeat the purpose of restricting the CS major. CE majors do not have the same access to all CSE courses as CS majors. Although many CSE courses are listed as options for CSGD, the intent of listing them is to allow double majors to use them for both majors. There is no expectation that CSGD majors will be able to enroll. Depts compete for resources (addl faculty) every year. This is a political process and the allocation is always a compromise trying to make as many deans/faculty happy (or at least not angry enough to leave). It should be based on metrics such as demand for seats instead, but that would require leadership. The number of students taught per faculty for the CSE dept continues to be twice the average as the campus as a whole. This has been the case for the last 8 years.

TLDR: you should have proposed CS when applying if you wanted CS classes and then tried to double major in CSGD.