More efficient vehicles have higher variance, period.

We once had a truck that would get the same mileage empty vs towing a few thousand pounds. Suffice it to say, that mileage was dreadful.

That's clearly not the problem here. Most EV makers can estimate range just fine, it's almost only Tesla that lies so much about it.

This is because most vehicles have a “reserve” of 1.5 gallons. So even when the gauge hits E you still have about 1.5 gallons at current MPG to make it gas station. This is get drivers to refuel sooner and not run the fuel pump dry which can cause major damage and be expensive to repair.

Isn't that by design? Some law requiring that computer needs to warn you about low fuel level while you still have enough of it to get to the nearest gas station?