I would say that the average person could fishhood someone and tear that lip up, or put their fingers in someone's nostrils or on their ears or eyes and tear it up. Although gruesome and not something I like to think about, I'm sure that this constitutes the tearing of flesh and that many people can do this. I would also assume that with years and years of hard training on the hands would allow someone to have much more strength that would possibly allow them to tear into skin and at least dislodge muscles or other anatomy. Pending this cannot happen, then the sheer pain of being grabbed in specific places with the intent that one is going to tear it off might be an advantage. But I am a beginner student and have not trained for very long and so I cannot say to the effectiveness of this. I also have no knowledge of how the eagle claw people train to do this but I believe that tearing flesh is a very possible thing with enough training. Many people of a good statistic cannot do a jumping inside crescent kick, but if they trained long enough it would be second nature.