In Step Six Bill W. uses the term "defects of character," but in Step Seven he uses "shortcomings." Why did he use two different phrases?

Bill W. used "defects of character" in one Step and "shortcomings" in another Step because he felt the terms to be interchangeable, according to a March 1963 correspondence. In another correspondence from November 1965, Bill stated that he did not want to repeat phrases twice in succession, so he substituted one phrase for another.