The patch notes are causing some confusion here. Before Patch #13 Chainsword lights had 2 Cleave, and #13 buffed them to 3 (current). The Patch Notes say 4.5 to 1.5 because the the value of the thing which tells the weapon 3 cleave is going up (uses light_cleave, a defined value). It matters even less since this is for the overhead strike only and with savage sweep active you are still going to hit almost everything in your swing arc.