ACT to SAT Conversion

The UC’s posted the freshman admission profiles for the admitted freshman for fall 2017. I was looking at the ACT scores and comparing them to the SAT scores and it seems like the ACT scores are higher than the SAT scores. Is there a reason for this (Is the SAT a harder test?)? If you use the prep scholar conversion, the SAT and ACT scores do not match up.

http://admission.universityofcalifornia.edu/campuses/san-diego/freshman-profile/index.html

Thanks.