I won't speak for Gen4 Prius, but that is not true for the Gen3 Prius. For Gen3, PWR doesn't change the propulsion system at all. It is just a different tuning of the user interface, at the gas pedal. It changes the touch and feel to the driver, but the underlying power available at the engine and transaxle is identical. Did the article you read describe some other implementations other than the Prius (e.g. Lexus or Highlander)? Was it specific to the Gen4 Prius?