Interestingly, it is the Left faction of San Francisco politics that have been slipping clauses like that (allowing legislative amendments, but requiring an estimated percentage that would overcome the current opponents and requiring amendments to “further the purpose” of the act) into local initiatives recently. June 2018 Proposition F (free lawyer to tenants facing eviction, which is a policy that both sides supported), allowed the BoS to amend “if the amendment serves to further the purpose of this Initiative” https://webbie1.sfpl.org/multimedia/pdf/elections/June5_2018.... Then in November 2018 Proposition C (double the gross receipts tax to fund homelessness, which is a policy that only the Left minority at the time supported and the Mayor opposed), allowed the BoS to amend “by a two-thirds vote but only to further the Findings and intent” https://webbie1.sfpl.org/multimedia/pdf/elections/november6-... In Nov 2019 Proposition F (increase disclosure requirements political ads, supported by the Left faction of the BoS) similarly had a nonstandard amendment procedure calculated to include the Left faction’s estimated percentage https://webbie1.sfpl.org/multimedia/pdf/elections/November5_... The failed rent control enabling California initiatives (Proposition 10 Nov 2018 https://vig.cdn.sos.ca.gov/2018/general/pdf/topl.pdf#page=83, Proposition 21 Nov 2020 https://vig.cdn.sos.ca.gov/2020/general/pdf/topl.pdf#page=29) as well as a millionaire’s tax to fund mental health (Proposition 2 Nov 2018 https://vig.cdn.sos.ca.gov/2018/general/pdf/topl.pdf#page=13) also contained 2/3 supermajority amendmendability.

So basically the authors of Proposition 22 took this clause that the Left has been evolving in San Francisco anti-business initiatives and copied it to their pro-business California initiative (changing the supermajority requirement to 87.5% to overcome the 73% who supported AB5), and this clause is contributing to the downfall of their own initiative. Ironic!