An issue with Spoils of War passive

Just a little issue that isn't significant breaking to the game.

As usual as I go bot lane support Sion, I tend to yell at the enemies with their own minions and I noticed when the minions die from the shock wave it doesn't proc the spoils of war passive.

Now when I talk about the dying minion I mean the initial one who takes the first projectile before being launched. I haven't witnessed subsequent minions who are hit die so I wouldn't know if they trigger the passive anyway.

Whether or not if this is a bug I thought it would be necessary to post it here since I wanted a few answers.

Thanks for reading!