Shaco's Jack in the Box does not proc spell effects (Rylai, Deathfire Touch)

This assumed bug has been around for a very long time. At first I thought this wasn't actually a bug, until I realized that Zyra plants, Heimer turrets, Teemo shrooms and Nidalee traps all properly proc every single spell effect in the game.

• Reproduction steps: Buy any spell effect item (Rylai, blue support item line, Luden's Echo, Runic Echoes, Liandry's Torment, Morellonomicon) or take a spell effect Keystone (Thunderlord, Deathfire), have your jack in the box hit an enemy champion and watch if the appropriate spell effect procs.

• Expected result: As with Zyra plants, Heimer turrets, Teemo shrooms and Nidalee traps, the boxes will properly apply spell effects.

• Observed result: Not a single spell effect in the game is applied on Shaco box attacks.

• Reproduction rate: 10/10