In my experience, I tend to get probably 250-ish miles on a 320 mile charge,

That's a 28% exaggeration in economy.

You're putting a certain amount of electricity into that car, and you are being told that amount of electricity is good for 320 miles. You're only getting 250 miles from that. Everyone else is only getting 250 miles from that. The only people supposedly getting 320 miles of range from that charge are the salespeople convincing you to buy it. Misrepresentation of the distance you can travel on a battery is no different than misrepresentation of the distance you can travel on a tank. You're just multiplying the MPG by the size of the tank, or the kWh/mile by the battery capacity.

Suppose I buy a sedan with a rating of 32mpg. But I'm only getting 25mpg. I put 10 gallons in the 10-gallon tank, expecting to drive 320 miles, but I have to stop and put another 10 gallons in after 250 miles.

Everyone else who bought the same sedan is getting 25mpg. Meanwhile, my other car, an SUV from a different manufacturer, is also rated 32mpg, and actually gets 32mpg. Everyone else who bought that SUV is reporting pretty damn close to 32mpg.

Clearly, the manufacturer of this sedan is pulling something shady. It doesn't become less shady when the sedan is burning gallons of diesel instead of gallons of gasoline. Or gallons of propane instead of gas or diesel. Or cubic feet of natural gas or hydrogen instead of a liquid fuel. Or pounds of steam instead of a combustible fuel. It doesn't become less shady when the sedan is consuming kWh of electricity instead of a mass or volume of a physical substance.