it's more to do with keeping the centre of gravity in the middle and low for best handling.
the
Big Bear has a big motor and a big battery, of roughly equal weight, so the logical thing to do is to put the motor to the front and the battery to the rear to balance their weight or put both in the middle like the
Woosh Sport CD. The additional benefit of having front driving is no broken spokes, big rear hub motors put a lot of stress on the spokes and tend to break them. Front driving motor is suspended - keeping stress on spokes even and low and less vibration too.