I suppose I could see how that could math out, assuming the engine running at an appropriate RPM to transmit to the wheels isn't less fuel efficient than an engine running at an appropriate RPM to generate electricity.

That's exactly what the car does in real time. My Toyota switches constantly between the ice engine transferring energy to the electric motors and the electric motors turning off when they are outside of their most efficient range.

It has an onscreen graphic to show you while you drive for the curious. It has another screen that gives you a driving score to encourage a driving style that maximizes efficiency like having the battery recharge more by braking longer and smoother.