As a product of the STEM post-SAT UC system (UCLA ‘26), I never personally experienced “middle school math” being taught or a lack of mathematical understanding.

I’ve had my fair share of classes which throw you into the deep end and not many which coddle you. Never seen any professor teaching middle school mathematics. A lot of professors started off with a vague idea of prerequisites, covered the basic ideas and usually go straight into the deep end with new material. It is up to the student to make sure they are acquainted with the prerequisites, go to discussions or office hours to ask TAs or the professor, or just drop the class and do it next quarter (without penalty). At least in my four years at UCLA, we have ample opportunity to do it and the TAs are 90% empathetic towards “stupid questions.”

So in my personal opinion, I think profs shouldn’t be wasting time teaching basic math and there are more than enough opportunities for the student to learn it at their time in the UC.