I just assumed the centre one-way was to stop the belt spining off power, reducing the amount of friction in the drivetrain.

Oh and by the way, on power the front one-way acts like a spool, so both front wheels get equal power. Off power they can spin at different speeds, as they are free wheeling.

Try holding one of the front wheels when under power, you can't as it will still spin, as there is no diff action, unlike at the rear where you can hold a wheel, and the other side will spin.

Ed