Unlike other AT controls (like 727) the relationship WRT motion and effect between the throttle linkage and the AT linkage is not linear.
There is a complex trigonometric relationship between the 2 motion paths that is not possible to achieve by attaching the TV cable to the carburetor linkage. The key is that the point of rotation on each half at idle is different, so the range of motion is not symmetrical.
http://purplesagetradingpost.com/sumner/techinfo/700R4p1.html
Does it work? Evidently well enough not to fail, but not the way GM intended.