[Gameplay Bug] Sion's Roar of the Slayer and Rift Herald

Sion's Roar of the Slayer (E) ability is able to use its minion pushback ability on Rift Herald, who is supposed to be immune to CC abilities like hooks, knockbacks, and other various abilities of this nature.

This is a 100% reproduction rate on his base skin at the very least; I don't own any skins for Sion to see if it works on his other skins as well, but I would assume it does. Have tried with a couple others things, including Blitzcrank hooks and the like, and it didn't work on it. Sion's E is the only thing I've found that works. Not necessarily game-breaking, but it could have adverse affects in ranked play if it gained more visibility because this can be used to reset the Rift Herald if you push it backwards and out of the pit, which would make Sion the ultimate top laner for deterring the opposing team from gaining Rift Herald.