The caster is adjusted by moving the top of the strut fore and aft (usually aft) after the spot welds are drilled out in the upper alignment plate. The subframe should be centered with the provided alignment holes in the subframe and unit body, but the subframe can be relocated to correct for uneven camber from side-to-side. The SF in my car is moved laterally to allow the camber on both sides to be within spec.
The device in the link looks like a non-straight, adjustable strut rod. That rod is mounted between the spindle and the subframe at an angle. Adjusting its length would affect not only the caster, but the camber and toe-in too. Not a real good idea since there are better methods available to adjust the caster.
