Jerryr: A question for you (and anyone else): Since we still don't have sufficient widespread EV fast charging infrastructure in the US, I think one of the major reasons this portable EVSE uses a 14-50R outlet (whose neutral is not used) as opposed to a 6-50R outlet (which has no neutral) is that 14-50R 50a outlets (unlike 6-50R outlets) are commonly available at RV campground sites -- which makes many longer trips more feasible if you're carrying this EVSE with you. These RV outlets, I believe, are wired with AWG 6 wire and use 50a circuit breakers.
My question is this: Would you hesitate to use these outlets with this EVSE to charge your Leaf because the circuits don't use a 40a breaker? A 50a breaker appears to adequately protect the AWG 6 wiring's insulation (from overheating damage) according to NEC. If the answer is "no", then why not use a 50a breaker rather than a 40a one for a similar 6 AWG circuit at your home? And while you are buying a breaker, why not buy a GFCI type which adds a significant margin of safety? (Also note, I believe, that the latest NEC requires them for portable EVSEs like this one.)