[Bug] Earthbound Voltaic Staff Works From Inventory

Issue: The Earthbound Voltaic Staff (unique) has the unique property that killing shocked enemies leaves sparks on the ground. This works while the staff is unequipped, and in your inventory. The spark skill is still not listed in my skill list, so I can't modify it, and it's unclear if the effect is visual only or real.

Steps to reproduce: I equipped the earthbound voltaic staff, then moved it into my inventory, and thereafter at least many shocked enemies which I kill drop a spark.

The screenshot through steam can be found below (doesn't seem like image pasting works on these forums?). In the image, there's clearly a spark projectile (next to the Morning Star common drop) despite the staff being completely unequipped. I do not have spark socketed in my skills.

https://steamcommunity.com/sharedfiles/filedetails/?id=3578578042