Not quite sure what you are getting at, but if you are talking about the parallel linkage between the bucket cylinder and the bucket then here's my understanding. The parallel linkage provides two advantages; 1) it gives the bucket cylinder more leverage for breakout work and backdragging, and 2) it eliminates the pinch point created when the bucket cylinder rod is attached directly to the bucket. With the bucket cylinder rod attached directly to the bucket, material (especially small stones) can spill over the bucket and "pinch" between the rod surface and the bucket causing damage to the rod which eventually damages the seals in the cylinder causing them to leak.
Generally economy built loaders use the direct connect while a high quality loader will use the parallel linkage.
I hope this answers your question.
OrangeGuy