It's a valid point. The drag doesn't go up linearly as you accelerate but exponentially. So driving 5, 10, or 20 miles per hour faster at highway speeds has a huge impact. Your speed goes up by a few percent but the drag goes up a lot more. Also nice to keep in mind if you are driving a petrol car. Because the difference comes out of your pocket and the physics works the same way.
The estimate the car gives you adjusts to what you are actually doing. So if you drive uphill very quickly (which is tempting because of all that wonderful torque you have), that number will get very low quickly. If you drive a really heavy car, physics dictates that you will use up a lot of kwh. The estimate will recover a bit if you level off for the remaining kwh. And you might even get a few kwh back if you go downhill via regenerative braking. But not all of it. It's probably merely reducing the number of kwh you lose rather than adding a lot back.
A more useful metric than range is miles per kwh at different speeds or under different conditions. The amount of kwh your battery has is a constant; but miles you get per kwh will vary depending on what you are doing. Teslas are normally around 3.5-4 miles per kwh on highways, which is pretty good for cars that size. But of course it matters how fast you are going. That puts them around the 200-250 miles range many people are reportedly getting; if you account for battery degradation, temperature, etc. and assume a 65kwh battery. Some recent cars are getting a lot of gains from improved aerodynamics and battery management. E.g. Kia is doing some great stuff on that front.
Also having less battery actually improves the miles per kwh number because there's less mass to drag around. Shoving 200kwh in a big truck makes it really heavy and combined with poor aerodynamics probably would make for less than stellar range than you might hope for. Probably you're getting less than 2 miles per kwh. So, more than triple the battery but nowhere near triple the range. And it makes the truck really expensive too. And you'll have to buy a lot more kwh to go the same distance.