I cannot answer since I do not work in admissions however, if the UC waitlist movement had an impact at SLO, historically you would have seen some admits by now. More than likely they have reached their enrollment target. I have not seen any posts where an SLO enrolled student has given up their spot after being admitted to a UC or another choice school.
Perhaps they are waiting to do all their waitlist admits in one wave, but it does not make much sense since many students have moved on and are happy to stay with their current schools.
I do not know the rationale of why SLO is dragging the waitlist process out but again, they that is how they do regular admissions.
Based on their waitlist history, if there are spots available, they would have admitted students already. Only time will tell and most people do not post on social media.