One important thing you are missing, there are two different estimates being referred to. The "miles remaining" display on the battery charge gauge (which can be toggled to show percentage instead) and the trip planner / navigation estimate. The trip planner is very accurate, you can view a burn down charge of realtime estimate as it changes while you drive and it says what component contributed what % to deviate from the initial estimate. The "miles remaining" display is an imaginary number that is only meaningful if you are driving the same highway mix as the EPA test in the same climate conditions
This is correct. If you tell it the destination the range estimate is astonishingly accurate. And it will list all the reasons it turned out to be wrong down to what fraction a headwind impacted range.
