Well, ryung's TvZ is pretty good imo, especially now since tanks are back in the meta. Also, while it's true, neither would byun gonna win any good tournament with that kind of performance.
Since the latest patch, Byun's winrates vP and vZ are far, far better than Ryung's.
Byun TvP: 74%
Ryung TvP: 48%
Byun TvZ: 70%
Ryung TvZ: 44%
Ryung is a great TvT sniper, but his other matchups are below 50%.
It's true that if Byun played as poorly (losing 20 army supply for nothing) as he did against Ryung today, he would almost certainly lose to anyone else in the Ro16. But those kinds of mistakes are random and therefore unpredictable. It's logically fallacious to assume that he would have made a mistake against a different opponent if he did not against Ryung.
I feed off salt like this. Sad thing is ByuN wouldn't have won the GSL regardless if he would lose to someone who's "so bad" according to you? Think before you post.
Don't forget to drink lots of water. Gotta stay hydrated.