It does allow for the largest radius rotor, by locating the caliper inboard, so a braking advantage. On a cast motorcycle wheel, I don't think rim condition really comes into play.
The perimeter disc brake was supposed to have better cooling since a greater portion of the disc was exposed to the air. It also supposedly allowed for a lighter front wheel since the spokes don't have to deal with braking forces.
Dunno how much a lighter front wheel helps on a rigid front fork like this though..