Electric motorcycles definitely have advantages in the bush, and I would like to see more of that! Apart from the advantages mentioned by that site, the low speed torque and clutchless nature of electric drives make it a natural for rough terrain.
The bikes you linked to show their purebred sports/competition pedigree. Workhorse motorcycles for the rough look very different, for instance the German and Russian sidecar bikes of WW2, and the scooters used in farms today in SE Asia (especially Vietnam) often tow trailers or have sidecars and they handle offroad conditions well enough. Interdiction in flagrante delecti is where speed and agility are paramount, but I don't know how often that occurs, or if it is desireable.
They sure do look like fun though.