Mordekaiser's True Experience

This is something that I have questioned for the longest amount of time. When Mordekaiser kills an enemy unit using an ability with an ally champion nearby, he receives extra EXP. This is also increased for every ally champion nearby. From what I have seen, there is no tool tip on his Passive, Q, W, E, or R stating that he receives this.

I get it how he was reworked to be a melee ADC in the bot lane, so this little EXP boost is kind of good because most bot laners are ranged, or has more range on their abilities.

I don't know if this should be removed or kept, because I have no idea on how to balance a champion. So I'm gonna leave it to you guys.