But in his intro to the Small Catechism, Luther says this, "In the first place, let the preacher above all be careful to avoid many versions or various texts and forms of the Ten Commandments, the Lord's Prayer, the Creed, the Sacraments, and such. He should choose one form to which he holds and teaches all the time, year after year. For young and simple people must be taught by uniform, settled texts and forms. Otherwise they become confused easily when the teacher today teaches them one way, and in a year some other way, as if he wished to make improvements. For then all effort and labor that has been spent in teaching is lost. Our blessed fathers understood this well also. They all used the same form of the Lord's Prayer, the Creed, and the Ten Commandments. Therefore, we too, should be at pains to teach the young and simple people these parts in such a ways that we do not change a syllable or set them forth and repeat them one year differently than in another."
Luther did not change the commandments. He first stated them, and then asked, "What does this mean?" IMO, that's quite a bit different than rewriting them.