I believe what DITB means - while you are on your way, running navigation, the instrument cluster should also show how much (rated) range will be leftover after the destination is reached, based on extrapolation estimates - is pretty much the same as knowing the current "estimated" range left.
Yes, exactly.
Example:
50 miles to destination
70 miles rated range
At the speed I am going (or because of uphill, headwind, driving style or whatever), I am currently using more Wh/mile than the rated range - and will arrive at my destination with 10 miles rated range.
THAT is what I want to see. NOT that I have 70 miles rated range left RIGHT NOW, but rather how much is my rated range estimated to be, once I reach my destination, in this case 10 miles.
As long as that number stays above zero, I should be good to keep going at that rate (unless last part of the route is a steep upslope, which isn't counted into the Nav calculation!)