[NeilBlanchard]

Power source is not the same thing as an energy source. And engine or a motor is a power source. Fuel or electricity is an energy source.

Two different types of power sources, combined in some fashion i.e. hybridized is the definition of a hybrid.

In a standard Prius (not a plugin) even the regenerative braking energy came originally from the gasoline burned earlier. So, if your definition of a hybrid (two different energy sources) is correct, then how is a Prius a hybrid?

The original Porsche was a series (aka serial) hybrid and all the energy in the batteries came from the engine. And a Prius is a parallel / series hybrid, since it can operate in EV (using energy put in the batter by the ICE and/or regen), ICE, and combined, too.