From my observations of them they do nothing at all. There was just as much wheel spin before as after fitment.
Using a bit of simple physics, look at the leverage ratio between the wheel radius and the effective radius of the gear surface on the housing. Say 300mm/15mm or 20:1.

To get 1.38kg/m (10 ft/lb) of torque at the wheel, you would need a torque of 27.6 kg/m on the side gear. This means a loading of 1840 kg on the gears and housing.

1.38 kg/m is a dead loss anyway as this does virtually nothing on dirt. To get up to the 40 ft/lb breakaway force on the clutch pack required from most LSD's you would need 7360 kg of spring loadings on the gears : ) Now I'd like to see that! Also when a normal clutch pack lsd starts to get speed differential between wheels the spider cross starts to lock up the clutch pack against the housing allowing the diff to drive on the one wheel.
I think the phantom has got a grip on something very personal and its definately not giving traction to the wheels