[SpicyLemonZest]

California's community college system is designed to provide the "remedial year" you propose, and this is a well-known pathway among California high school students and admissions counselors. If a high school graduate wants postsecondary education but isn't quite ready for a rigorous college curriculum, they sign up for the local community college. If they do very well, the CSUs and UCs accept and encourage transfer applications; if they find it's still not for them, then they take the associate degree and move on.

Freshman admissions at UC San Diego are for a different group. They have a 28% acceptance rate, not the most selective in the country but far from taking anyone with a pulse. The admissions office intends to reject people who doesn't know how to do basic math, letting them know that this isn't the right pathway for them, but they're not able to do that reliably without standardized tests.