I don't know about saying the two barrels shouldn't shoot to the same point. Say I have a medium bore that puts both barrels in one hole at 100 yards. At 200 yards the two holes will be the same distance apart as the muzzles were at firing. At 300 yards they will only be twice as far apart. (Neglecting all other variables of course.)

If the barrels are set to shoot exactly parallel then the two bullet paths are the same distance apart as the muzzles were at fring for the whole distance. They will be farther apart than the one holer all the way to 200 yards.

Don't forget that due to jump the muzzles will be farther apart at firing than their actual seperation on the rifle.

It would make life a little simpler for the regulator if he sets the barrels to shoot to the same point.