I believe you are correct…unless there have been any recent changes. A C- is the equivalent of a NP in the P/NP format so accordingly the UCs treat it as not passing.
Interestingly the CSUs treat a C- as a passing score but won’t allow a student to use it as prerequisite credit. (i.e. You passed Calc I with a C- but can’t take Calc II without retaking Calc I)