Per your ref that I agree
Per your ref that I agree with: At about 70 mph, the Chevy’s motor is starting to spin too fast to be efficient, so the ring gear unlocks from the case and locks to the smaller motor/generator. Now both e-motors spin, propelling the Volt to 101 mph turning at reasonable rpm in electric mode.
Also in your ref article: Once the Volt’s battery is depleted, the engine fires up and clutches to the generator to produce the power required to drive the car. Above 70 mph, when the generator couples to the ring gear, the engine gets a more efficient direct mechanical connection to the wheels. In defense of Chevy’s earlier stance, the only way this gas engine (or the Prius’) could ever drive the wheels without lots of help from the battery is if you somehow MacGyvered up a way to jam the sun gear to a stop.
First, the battery is never depleted. Its state of charge (SOC) can get down to 20 percent. If it was totally depleted then it couldn't do what the next paragraph says, works with the IC engine.
Second, when the IC engine clutches to the generator, it is supposed to in order to maintain the state of charge on the battery which is still feeding power back to drive the e-motor.
It appears per the ref article that this so-called more-direct situation occurs only above 70 mph at low SOC battery, where BOTH the IC engine and the e-motor drive the car because the e-demand is super high, making it more like a hybrid at that point at worst case. So, that reads to me as a design that protects the e-motor from spinning too fast and drawing too much from a low SOC battery. Even in that situation, the IC engine never drives the wheels alone without the e-motor; hence a hybrid-like condition. Still, I will conform with GM and report back.
According to your MT ref, bottom line still is: the Volt is still an electric vehicle driven primarly by the electric motor. Unlike a Prius that uses an e-motor for boost, the IC engine for the Volt, aside from recharging, merely adds boost in select high speed aplications when it is most efficient and protective of the e-motors do so.
Good catch on the MT article.