I've heard rumors that the EPA test drives until the car won't go any further. What that means for the actual battery, is the point where the modules can no longer provide enough combined power to propel the car forward. Some have tried to drive beyond 0% to varying degrees of success. My guess is that for EPA testing, Tesla allowed them to use the 4kwh brick protection and take the battery to nominal charge = 0 to get their EPA rating. But in practice, they make 4kwh nominal 0% so that drivers don't dip into it. And dip into it at their own risk because you could have a module imbalance that the car would shut off at 2kw or some other number below 4, for to the high voltage battery not having enough power to power the car at the required voltages any longer.But the problem is, the EPA test determines what the rated range is, which is actual miles driven on a full charge, and that doesn't include the buffer.
Again, our car could go that 100% rated range IF you could use all of that 4kw @ 290 watts per mile consumption. But not only is it not recommended, you also run the risk of the battery crapping out due to reduce power output.