I doubt it, when I had Messi he would miss a lot of chances that even someone like Heskey would score. He would dribble past 3 defenders be one-on-one with keeper and still miss. It even got to the point where I had to fine him for poor form and constantly criticise him. In his report it says he's consistent and good in important matches and all his stats are perfect for most attacking positions and roles. So it clearly shows that SI have messed around with these guys' hidden stats to make them not play as well as they should.
They havent. Because that's not how it works. They are set by the researcher. also you can see their hidden attributes in the editor