Dark Harvest apparently triggers on any ability regardless of dealing damage?

I was just playing Trundle and my pillar triggered dark harvest. Pretty easy way to grab stacks in aram.

But it seems wrong, and sheds some light on why DH also makes Pyke's execute have a higher threshold. DH doesn't care if the ability damaged the target, it just cares if the ability "affected" the target.

This doesn't really match the tooltip, which states that it triggers on damage dealt.