Ah yes, the old confusion between single phase and three phase, and the US' habit of 20% de-rating on continuous loads (which EVs are). So yes, it's a 50A plug, on a 50A breaker, but you only get to charge at 40A. The gen 2 connector still has a 50A plug, but will only charge at 32A (corresponding to a 40A breaker). It'll be interesting to see if Europe gets a new mobile connector too when the Model 3 arrives there. I kinda doubt it.