I recently heard a car commercial on radio which stated that this car had a feature that automatically shifted the transmission to neutral when the car is stopped, for example at a traffic light. By doing this, you saved gas. Can this be correct?
No. There would be no gas savings from such a scheme.
The engine idles at the same speed at stops, regardless of what gear you’re in. Nowadays, you only meed mention that something “saves gas” and everyone’s ears perk up.
No benefit from this.