The "Bandit" Mastery does not working properly.

In the description, the "Bandit" mastery said:

Gain 1 Gold for each nearby minion killed by allied champions. Gain an additional 3 Gold (or 10 Gold if you're melee) when hitting an enemy champion with an attack or spell (5 second cooldown)

However, when I hit enemy Champion with a spell, no matter it is single target spell, AOE or damage over time, I never see "3g" or "10g" occurred.

The effect only occurred when I do Auto Attack.

If this is a bug, please fix it.

If it is not or it is intended, please change the description.