When the wheels are turned, yes, contact patch changes dramatically. But, when you are going down the road straight, two additional degrees of caster is not going to give you a noticeable difference.

 

the amount of caster changes the camber proportionately in off center steering. since you have 4+ degrees positive caster and specs are 6+ degrees you are wearing less tire while cornering right now. with the down side being a tendency to wander. I think this is called scrub radius. Mercedes Benz runs over 10 degrees of caster on some of there longer sedans for high speed stability and if you ever see one parked with wheels turned they are laying over quite a bit.