A dual pivot brake works best with the pads flat on the rim, not toed in. Brake pads don't normally get rotated, because most are designed for one orientation. If one end of the metal part holding the shoe is open, that end must face the rear. Otherwise your pads could come flying out of the brake. Maybe the pads were previously mounted incorrectly, and the mechanic changed them for that reason. Yes, they will eventually wear flat again, but could take a few months. If the squealing bothers you, go buy new pads.