The only thing I can come up with is that by spitting power between two axles the axle losses
are minimized over some operating range, so it may look like having a driven wheel minimizes RR, but in fact it's that axle efficiency isn't linear and can be optimized to some extent.
Edit- Jeez , I've had five beers and I'm talking about axle losses. I should just get a degree in ME and call it a day.
