It’s not using a single joystick, however. It’s using axis 2 and 3, which are on seperate joysticks and therefore take the 2 dimensional shapes of the joystick out of the equation, as each is only measured in a single straight line and combined together
The OP used axis 1 and 2, but with axis 2 and 3 you are correct.
I see, OP changed to axis 2 and 3 in a comment after yours with the visualization