I think there was a Renault that worked like this. I think the main issue is that you need a decently sized battery that can supply enough power or else the ICE needs to start every time you hit the gas pedal like was the case with the older Prius models and then you might as well connect it to the wheels and you can have a smaller electric motor.
But batteries keep improving and you can pull more power per kWh now. Maybe with solid state batteries this power train could become the more affordable option.
I’d say the index is actually an offset is a reasoning for explaining why it should start at 1. If index was an index, I’d just start at 1.
I don’t think any one is better than the other, but history chose 0.
That you can choose it in VB is probably the worst option :D