This is demonstrably false. If you get a brand new Tesla and charge it to 100%, the range on the screen will be the EPA range. That’s not a “rosy” prediction, that’s the prediction that companies must legally use in their sales material in the US.
Also, the BI article says this was 10 years ago, but the Reuters article opens talking about the Model 3, which was only released 5 years ago. But it’s coming from an unnamed source who claims it was a decade ago - not exactly reliable.