Well, that's not strictly true with EVs... the car and EVSE handshake and agree on the current. The right EVSE on your hypothetical 10A 240V outlet would work just fine (well, Volt will definitely do 12A on 240v, not sure it will handshake to 10A but it might ... somewhat depends on the car). You're right that you can't put a 40A 240V EVSE set for max power on that same outlet and expect it to work, of course. But a programmable EVSE or car (Tesla allows you to select the current) would work.Always remember the dichotomy of electricity: the source determines the voltage, but the load determines the current. This is why we need breakers or fuses. You can plug your Volt into a 50 amp 240 volt outlet but it is still going to draw what it wants, about 16 amps. On the other hand, you can plug it into a 10 amp 240 volt outlet and it will still draw that 16 amps, oops.