I think that Hahn and Christina's lack of teaching skills illustrates something that is well known and accepted -- not all talented people teach well. In order to teach effectively, you have to be able to take apart the process of doing something, and relate it to people who don't have all the knowledge that you do. Not everyone can do that. For people who are highly intelligent and can't relate to those who aren't, there's a very very easy tendency to just give up and say "oh, just let me do that". Both Hahn and Christina tend to display that sort of behavior. They're so focused on getting the job done that they don't want to have to slow down and do something else (teach) at the expense of getting the job done.