I'll say, if I'm guilty of not reading the article -- It's because I only read the abstract and conclusions. That's what I do when I want to speed read professional findings for just the cliff notes only.
The study basically concluded what I posted above, in their own words. In other words, "From the results we give, we cannot conclude anything about children with cochlear implants and their speech potential. But here is what we think: ---"
As for a conclusion about ASL or oral speech hindrance possibilities will have to be drawn in the art of opinions that vary from person to person, and possibly culture to culture until we can find a study that directly focuses on it.