Gnar transformation

Right, so I'm not too sure if this is an actual bug or glitch or something that was intended to be with the champion, but I've been noticing that when mini-Gnar's rage is full casting any spell will instantly turn him into mega gnar. I think this might be intentional with his q and w- but I've had times where I've tried to e over an enemy to quickly get behind them before the full transformation only to use crunch as mega gnar instantly. Anyone else have this effect or is this intentional?