From 2010, when the Karadima story began to get attention:

... Juan Carlos Cruz, a Chilean who is now a corporate executive in the United States, said that when he was a 17-year-old seminary student who had just lost his father, Father Karadima also used confession as way to abuse him, touching his genitals and kissing him on the mouth. He said that in confession he had told Father Karadima that he was confused about his sexuality. He said the priest took advantage of that knowledge to intimidate him into remaining silent ...
http://www.nytimes.com/2010/04/23/world/americas/23chile.html

And from Wednesday:

... Cruz alleges Barros not only knew about the abuse he and his peers suffered at the hands of Karadima, but that he was actually in the room when it happened ...
http://www.cbc.ca/radio/asithappens/as-it-happens-wednesday-edition-1.4491266/why-this-chilean-abuse-survivor-refuses-to-accept-pope-francis-apology-1.4491284

Puting those side-by-side indicates Karadima took advantage of confession. But in Roman Catholic practice, confession is private: Barros should not have been close enough to hear what was going on; and (depending on the size of the room) may not have been close enough to observe anything clearly. It is, of course, possible that is not the whole story, but the question reasonably arises why the 2010 report doesn't implicate Barros