Whenever the servo arm and the pushrod do not make a 90degree angle, the pushrod will be moved more in one direction than the other.
Same situation where the pushrod connects to those torque rods in your picture.
AND same situation where those torque rods bend down inside the wing and go out into the ailerons.

The servo does its moving in a circle. The circular motion winds up being sort of a straightline push and pull for the pushrod. When the pushrod is connected on the servo wheel or arm at a 90 degree angle, the pushrod is basically at the center of that circular motion it will see when being pushed or pulled. So when the servo moves 45degrees either way, the pusrod moves the same amount both directions. But say you were to connect the pushrod on a servo wheel at the 45degree location.

Clockface example.......
Pushrod connected at 3 o'clock.
Servo move to 1 o'clock or to 5 o'clock and the pushrod moves the same UP and DOWN.

Now connect the pushrod at 1 o'clock.
Servo moves from 1 to 11. How far would the pushrod move? Almost wouldn't move up and then would move just as little back down
Servo moves from 1 to 3 and the pushrod moves down as much as it did moving from 3 to 5 when it was connected at 3.
That's how people get differential out of their pushrod rigging.

And that's also an example of what happens when the angles aren't 90degrees.