Dr. Mustafa Zayd, in his book النسخ في القرآن الكريم, volume 2, pages 127-128 (item 862), writes that Abu-Ja`far An-Nahhaas reported the claim that
was abrogated by the Sunna, since the Prophet (PBUH) adopted Zayd ibn Haaritha ibn Shuraaheel Al-Kalbi after freeing him from slavery, and he also made him brother of Hamza ibn Abdil-Muttalib (the Prophet's uncle), may God have been pleased with him. Reported by Al-Baghwi in his book معالم التنزيل, volume 7, pages 499-500, and by Ibn Katheer in his exegesis, volume 3, page 466. Ibn Katheer asserted that 33:4-5 abrogated the practice of the Arabs prior to it.
Dr. Zayd says that At-Tabari, Ibn Al-Jawzi and As-Suyooti did not address the abrogation claim at all in their books, but Ibn Al`Arabi did, in his book أحكام القرآن, volume 3, page 1495. He rejects the claim. But he only addressed the claim that 33:4-5 abrogated the practice of the Arabs before it.
If my memory serves me right, I recall reading narrations that the Prophet (PBUH) stopped the practice of virtual brother and adoption, so the claim is the other way around, isn't it?