Why doesn't 17:13 say, "If he commits iniquity"?

The chapter doesn't say, and this answer doesn't guess. 2 Samuel 7 has, "I will be his father, and he will be my son. If he commits iniquity, I will chasten him with the rod of men and with the stripes of the children of men" (2 Samuel 7:14), and then, "but my loving kindness will not depart from him, as I took it from Saul, whom I put away before you" (2 Samuel 7:15). 1 Chronicles 17 has, "I will be his father, and he will be my son. I will not take my loving kindness away from him, as I took it from him who was before you" (17:13). The words about iniquity, the rod and the stripes aren't there, and Saul isn't named. The book does have an "if" later, in David's words to the leaders of Israel, where he gives the LORD's words about Solomon: "I will establish his kingdom forever if he continues to do my commandments and my ordinances, as it is today" (1 Chronicles 28:7). The book doesn't link that verse to 17:13, and neither does this answer.