Battlecast Cho'Gath's E uses the default skin's sounds.
I've just recently purchased Battlecast Prime Cho'Gath, and after playing a match to try the skin out I've noticed that the sounds for Battle Cho'Gath's E are the same as the classic skin's. This is strange because before Cho's E got mini reworked the sounds on Battlecast Cho's E were completely different from the default skin, so it doesn't make much sense that they're suddenly gone now.
I am not sure if this is a bug or intentional but I just thought I'd point it out.