It’s not though. Range is determined by how much battery is in a car, I could build a car with 500km worth of Ni-MH but it would be mostly battery.

Does the same car with 500km worth of lithium batteries have more or less trunk space than 500km of these batteries? I have no idea. I do know the sodium batteries will weigh a bit more, because the article actually gives Wh/kg - and that makes sense since sodium the metal is denser than lithium, but the headline is meaningless.