Earlier quoted context omitted.
Those clients could be doing a better job - when twitch starts playing an ad on the main stream, they also provide a secondary stream that shows the actual content.
i believe that secondary stream is used for picture in picture so its lower quality, like 480p or something
A third-party client has room to make a dramatic improvement on the twitch experience by not dropping audio while you make the switch from the ad stream to the content stream.