AFAIK proposals (e.g infamous prop 13) cannot be overturned by legislature at all, even with 100%. So 7/8th is actually easier than default.
"The California State Legislature may not amend or repeal an approved measure without submitting the change to voters. However, a ballot measure may include a clause waiving this protection either entirely or conditionally."
https://ballotpedia.org/Laws_governing_the_initiative_proces...