God King Garen Squeaky Sword

So after playing around with the skin and watching others play with it, I've noticed that every now and then God King Garen's Q attack and regular auto attack will sometimes produce a squeaky/slippery sort of sound effect, which is really unfitting for the skin.

It happens twice in a row towards the end of that clip, (if you skip to 21 seconds you should be right before it happens) when he's autoing the tower.

It's not exactly a game-breaking bug, but kind of jarring when it happens and a little annoying. Curious if this is an intended sound effect or just some weird audio bug.