I don't think the author has ever seen the show... or at least, seems to be forgetting some pretty prominent things from the show regarding the article's subjec

I don't think the author has ever seen the show... or at least, seems to be forgetting some pretty prominent things from the show regarding the article's subject. There are countless references, especially in the early seasons, to the insanity of the "mad king" being the result of inbreeding. Even in-universe the fact that the targaryons had extensive inbreeding is believed to be the cause of many mentally-ill kings. Physical abnormalities aren't talked about as much from what I recall but the principle is the same. Also, Ned Stark arrives at the conclusion "this blonde kid couldn't have a black haired father" after reading a history of the baratheon family going back to the founding of the house and noticing literally every descendent had black hair. This presumably was included in the story to exclude the possibility of recessive genes appearing in the children but not the father.