Yes I know I’m quoting myself, but it is an actual question… I would love for some knowledgable person to address it if they can.
The reason I bring this up is that I myself went to college having only completed 3rd grade math. (I went to a weird hippie school.)
I had severe math deficits. But I was able to pass freshman Calculus (nobody thought to give me a placement test, and I didn’t think about whether I was ready for it). Because I had no idea about how I was supposed to do math and therefore solved problems in very weird ways, the math department convinced me to be a math major and recruited me to join their math competition team. The higher level math classes were better for me because I loved doing proofs, and because calculators and computers existed. I never really got over my elementary and middle school math deficits though. I am bad to this day at practical applied math stuff, and I had trouble helping my kids with their elementary and middle school math homework.
So I’m just wondering if some of these students have holes in their math knowledge that is being exposed specifically by UCSD’s math placement testing process focusing on grade 1-8 math?
(and just to be clear, I do not recommend going through life with big gaps in math knowledge! 
)
Edited to add: I also did okay on the Math part of the SAT, and I have no idea why! Maybe there were enough questions that only required logical thinking or good guessing 