Prop 13 (passed in 1978) reduced budgets substantially for local governments in California --- roughly 60% state wide [1]. Perhaps that's what they were referring to.
>>leafme+(OP)
It did not reduce local budgets by 60%, it merely reduced local government share of property taxes by (not quite) 60%, initially, as the Brown administration and Democrat legislature leadership clawed money back to state control.
(The local share of property tax was not defined in Prop 13; this is strictly how the Democrats in power chose to implement Prop 13.)