Air Suspension Conversion Question

Why will the Suncore 53F-30-HD Air Suspension Conversion Kit not work on a rear wheel drive 2001 Expedition-VIN 1FMEU15L31LB82811, but only on the 4WD version?

The reviews for the 2WD conversion kits is always negative with the expedition sagging afterwards. Will the mentioned kit be able to be used on the 2WD to give it more lift, etc?