Isn't an article necessary before the word "desk-dwelling"?
Usually, "a" would be before "desk-dwelling". However, he is speaking in a stylized way as though he is giving himself the label "desk-dwelling computer nerd", and comparing that to the label "the kind of guy who bikes to work". You can visualize this way of speaking my imagining him labeling the photos of himself that appear on the screen with "desk-dwelling computer nerd" and "the kind of guy who bikes to work".
Get more Native English Expressions >