And they include language in the bill that it can't be overturned except by a 7/8ths majority which would make it functionally immune to being overturned, ever.
Is that even possible?! I’m not aware of the ÇA constitution but bills in my state descend from the constitution they can’t exceed it. To do that would require a referendum to change the constitution. Which they are trying to do now by making a referendum to make voters vote 2x to pass (ie make laws take a long time and very expensive to vote in).
California ballot propositions have the possibility of amending the state constitution (see Prop 13 [1] as one of the historic examples), and once you're allowing that, anything is possible.
These initiatives amend the state constitution, so they can set any requirements they want. Prop 13 famously added a requirement for 2/3 vote to change it, and this was sustained by the US Supreme Court: https://en.wikipedia.org/wiki/1978_California_Proposition_13