Probably, people in later generations thought that, because Norimune was the head swordsmith in attendance, he must have been the person who inscribed the chrysanthemum symbols; that is why Norimune's swords have been called Kikuichimonji.
おそらく後世の人々が御番鍛冶の筆頭を務めていた則宗だから菊文を切ったに違いないと考えた為に則宗の刀が菊一文字と呼ばれるようになったのではないかと思われる。