There's a couple of differences here. The 720 tornado kick takes a long time to develop and is usually easy to see coming a mile away. Getting hit with it by someone good at it is going to be rare. These new BJJ tactics and setups can blindside you out of nowhere if you're not ready for them.
Additionally, a 720 tornado kick is worth the same amount of points as a regular tornado kick. If it lands, you lose a few points and keep going. In BJJ, a well-executed technique usually gives you a submission (immediate win) or a positional advantage, which is much harder to come back from. Coming back from a TKD match where you're down by 3 means you need to land a couple of basic kicks on the opponent. Coming back from a BJJ match where your opponent hit a sweep into mount means you're down by 7 and you need to get out of mount before you can try to score.