You have to be smart to trade flow derivatives. Not only is it necessary to understand the product and pricing tools, but also you have less time to examine any given trade than your customer does, you have to deal with weird correlations and dispersions that were forced upon you by customers, your social skills and sixth/"I'm getting played" sense are just as much a part of your toolkit as are your math skills, and you aren't given too much leeway with mark-to-market p&l.

You probably noticed at GS that a risk desk won't put an employee in front of a book just because he got good grades at UPenn.