I've found the max range on the Hyundai Kona EV's is fairly accurate. It can vary quite a bit with stuff like AC/heat but generally in reasonable weather it gets close to what was advertised.
The MPGe Tesla advertised also is. Then they use that to correspond to % remaining battery.
All EVs get wildly different range depending on outdoor temps (I get 30% lower range in winter) and their hysteresis is way higher than an ICE car. But, their range numbers are accurate for when they are measured under ideal circumstances.
I regularly do better than rated range. Others have a heavy foot and do worse. Kinda par for the course.
One thing is to exaggerate the range in your advertisement material, which every auto manufacture does—especially since you need to meet veeery specific criteria to get the advertised mpg.
Another though is to rig your software to show misleading range to the people actually driving the fucking car, that’s either stupid or very shady.