I don't think (2) holds water as a reason that charging in accessible chargers is open to all. EV charging spaces are specifically treated as a type of parking spaces by the vehicle code, see
http://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=VEH§ionNum=22511.
When the article that you linked says that parking and charging are distinct, what they mean is that parking and charging are different services that both require disability accommodation. As a property owner who offers both parking and charging, it's not enough for there to be accessible parking spaces near the building, you also need to make sure that you have accessible charging stalls.
I agree that the suggested markings in that document are insufficient to make a legally enforceable disabled-only parking space, but it's not clear to me that this is by design. They are certainly very confusing to someone who doesn't know the specific elements required for such in California (which can vary depending on when the spot was installed!):
Law section
It all comes from the overloading of the ISA (wheelchair symbol) to not just mean "here's the accessible option anyone can use" (like for restrooms or building entrances) but also "reserved only for those who need it" in the context of parking spots. It seems the former interpretation is intended here, but then even the author of the doc you linked seems to be confused by this, as they state that the requirements for small charging stations (having at least one van accessible spot that needn't be labeled as such) result in an accessible stall "available to everyone and not limited to those with access license plates or placards", hinting that this is not true for the larger cases where the ISA is required.
I can see why Tesla installations sometimes include signage with explicit permission to use the accessible stall; it could help people worry less about getting into legal arguments over what the ISA symbol means...