I've heard a slightly different explanation.Driving on the left as we do you do more right handers than left handers because thats the way roundabouts work,and you also push the bike harder on right handers because they are safer than left handers.Get it wrong on a left hander and you stand to meet Mr volvo head on
The other thing is road camber.Going in a straight line the camber of a normal road will tend to wear the right side of the tyre slightly more.Apparently it all adds up to uneven wear.