There’s a few cleave breakpoints. For the Rapier’s lights/A&F falchion’s lights it let’s it cleave Marauders without having to stagger them first. Makes horde management very consistent, where as it can be kind of dicey for the Rapier/A&F otherwise (requires lots of pushes and such).
For range breakpoints it lets the Crossbow bodyshot Packmasters at long distance with 20% Skaven + 20% Monsters. I haven’t used this much so I can’t say if it’s useful or niche for the Crossbow since it bodyshots at close range.
For BoP it lets it 1 shot headshot Packmasters at close range without having to have Deathknell with the same properties as the Crossbow bp above.