User blog comment:Cajadehu/How Blackbeard stole Whitebeard's Devil Fruit Power: Theory/@comment-13439417-20160502163030

I think the explanation is truly simple: When Sengoku said that BB could have two devil fruits because of his body constitution, he was directly thinking about the changes BB's body went through after eating the Dark-Dark fruit.

That fruit makes one able to absorb things. Quite simply, one is able to absorb other DFs and use them you know?

That would explain why he was waiting so long for that single DF no?