A long time ago, we were told that bump slashing had its power reduced by half and accepted it even though we noticed no difference in-game. Tydeus and I found that the animation frames it included were only for the soft bump when your horse is moving slowly, so we tested to see which animation frames accounted for knockdown and added that in.
Essentially, what we have now is bump slashing's intended damage from way back when it was first introduced and did nothing.
In the patch notes: Tydeus: Pike & Throwing Lance bonus vs cav. Bump slash nerf now includes knockdowns, not just soft bumps.