I don't know how much teaching styles have to do with it. I think the most effective teachers of the shot are the ones who can teach the physical mechanics best. I liken it to a pitching coach in baseball. The shooter who is most consistent in making the shot is the one who is focused and comfortable, and has a routine about his shot. For some, this can be seen in going so far as to make a jump shot out of it. Hal Greer was successful at this method for years. For others, it can be mental focus, such as was the case with JJ Redick.
Even though they were good at it, Chamberlain and Barry's underhand shot hopefully won't make a return soon. On second thought, if our guys can hit 90% with this style you won't hear me complain!