I couldn't find a clear cut California rule for this, but did find this document which is pretty recent and an official ca.gov website.
https://www.documents.dgs.ca.gov/dsa/access/EVCS_FAQ_09-20-17.pdf
"Are the ADA spaces ADA-only?
RESPONSE:
Standard accessible and van accessible EVCS (EV Charging Station) vehicle spaces which display the International Symbol of Accessibility (ISA), sometimes referred to as the wheelchair symbol, are generally understood to be reserved for the exclusive use of a disabled person displaying special license plates or a distinguishing placard."
Seems like the spot isn't available for people that don't meet the requirements for the disabled placards. I don't think I'd personally ever use it, but I certainly wouldn't leave my car unattended in that spot if I did.