No idea at all, but I would assume it simply moves a potentiometer left and right like many 270degree steering wheels use for left/right movement.
Yeah I agree, the motorcycle games I have played on have not had a forward/back motion, just analog left/right (+ hand throttle + handbrake).
Some bike games have the entire bike tilt over left/right, or some seem to have a pivot just behind the handbars - the handlebars stay fixed and the rest of the bike swings left/right behind it.