The description states that the player needs to use all arrow types. But from experience, it seems to be that the player needs to kill a mob with the arrow, not just use it/hit something with it.

👍

Maybe just some weirdness? I was watching Sevadus and he hit a mob with the last arrow needed and it didnt trigger by just hitting some mob, but he went and shot a snail with it (which one shot it) and it triggered.

I can't reproduce this. Works fine for me without killing the mob.
I'm assuming this is for SevTech so I'll try it there later today.

Works fine in SevTech too, was probably just some lag or something like that