Pimpon: A universal joint (U-joint..it's technically a cardan joint) is rather primitive compared to a say a CV (constant velocity) joint. Based on the pictures above, if you are trying to turn the short stub shaft with your hand at large angles it's going to be very difficult/impossible because of the basic properties of a U-joint.
When you flex a U-joint the output shaft rotation (compared to the input shaft) is not constant. The output shaft will rotate with a sinusoidal component....this will make it easier/harder to rotate depending on the position of the U-joint as it rotates when rotating at a large angle.
At large angles it gets quite hard to turn ......you can simulate this with a flex universal socket and a ratchet.
This is why most modern vehicles use CV joints, they run smoother and are more efficient.
Here are a couple graphs of the input to output shaft relationship