In fact, it is not dynamic labor saving, but static labor saving.

It should be noted that when people lift a cylinder, they don't hold it at its center of gravity, but at its bottom. In this state, people are equivalent to doing a fishing action, which requires not only an upward force, but also a downward force, so as to generate a moment and really lift it.

When the top plate rotates, as long as the speed is fast enough, you can even put the bottom on the bracket and suspend the top to keep balance! However, the force at the bottom has not been substantially reduced, and it is still equal to the total weight of the whole column and disk surface. It is not difficult for an adult man to lift the total weight of 50KG. Therefore, in a dynamic situation, lifting it up is easy to understand: the rotation brings not the weight reduction, but the shift of the center of gravity-we can understand this first, and the problem will not be clear in a few words.

To sum up: the rotating state saves torque, not upward force.