Your information is not quite right. At least it doesn't apply uniformly to all CSU campuses. Some (including Chico, Fullerton, Long Beach, Pomona, SLO) are considered "impacted" in that they receive more qualified applicant than available spaces, and so they require and use ACT/SAT scores.
See the CSU web site for details. Best is to contact each school to which you're planning to apply to make sure of application requirements and deadlines (including test scores when required).
From the CSU web site:
"Test scores are required unless you have a grade point average above 3.0 and are a resident of California. The CSU uses a calculation called an eligibility index that combines your high school grade point average with the score you earn on either the SAT or ACT tests. Even if you have a GPA above 3.0, it is useful to take either an SAT or ACT as the score may indicate if you do not need to take English and math placement tests after you are admitted and before you enroll at the CSU. The eligibility index for out-of-state students is higher and admission requirements for international students are somewhat different.
While SAT/ACT test scores are not required to establish the admission eligibility of California residents with high school grade point averages of 3.00 or above (nonresidents 3.61 or above), impacted campuses and impacted first-time freshmen enrollment categories often include test scores among the supplemental criteria required of all applicants to those campuses and enrollment categories."