With respect, I think you rather missed his point. He is not making an argument that "Tracy Austin is really that boring," though he does set the reader up for this thought, so that he can playfully turn on it on the way to his conclusion.

Your analysis is a gesture towards his conclusion: "And that those who receive and act out the gift of athletic genius, must, perforce, be blind and dumb about it - and not because blindness and dumbness are the price of the gift, but because they are its essence."

Moreover, DFW speaks of the cliches evident in the internal narratives of athletic genius as, perhaps, perceived by their speakers as simple truths, imperatives to be acted on or ignored, not reflected on.

He also specifically calls out as foolish the idea that gifted athletes are dim, citing examples of technical analysis similar to the ones you've mentioned.

Finally, this piece is very specifically about the physical techne of athletes in relation to their internal and external narratives, which I, and I think DFW based on this piece, do not find of a kind with musical genius.