I am sorry , I am not quite understanding what has been disavowed. The Book of Mormon is not talking about Africans it is talking about natives of the Americas who have always been able to hold the priesthood.
From Race And The Priesthood (as quoted earlier in the thread)
Today, the Church disavows the theories advanced in the past that black skin is a sign of divine disfavor or curse,
Cook is avowing the theory advanced in the past (in the Book of Mormon) that black skin is a sign of divine disfavour or curse.
I thought the disavowal was of the theory that dark folks in the preexistence were caught smoking out behind the barn when they were supposed to be in church.
No denial or apology for past racial distinction has been made or suggested that I know of.
I think the foot is stuck in the trap . That is a danger when you start out claiming to have all the right answers.
The escape route is the door.