They do back up their claims with research. The problem is that the research is highly variable in outcomes. Which is why they can only make an educated guess, because that's all the research can give us at this point. It's not some kind of failure on their part at all. It has zero to do with their education and everything to do with the current, available research.
Yes, I do know Deaf adults, with CI, who were language deprived. Some are not language deprived, and some are.
You are disputing the fact that some children who are implanted end up linguistically deprived, based on your statement, "I wouldn't say that children who receive CI are language deprived"
Yet the research literature states otherwise. There are children, with CI, who are language-deprived.
"I know some who get along very well as well as a number of adults who also get along very well with their CI's too"
I am sure you do, but I know a number of implanted adults who do not get along well. I am not saying ALL children with CI are language deprived. Some of them do great! While others end up language deprived.
Just out of curiosity- do you think I am pro or anti-ci?