I'm not a Kyokushin practitioner, but my understanding is that the technique was not invented for tournaments. That said, it's also not one generally useful for open combat as it is, as you note, a technique that can leave you in a bad position after the attack. Just to clear up one thing, if you miss with the kick, you are essentially doing a forward roll, which is a technique many martial artists learn to do on hard surfaces. Yes, you do face some additional risk from uneven or broken surfaces, but presumably that's part of what you consider when you decide whether to use it. And if you land it solidly, your opponent helps cushion the impact, so that helps there. What is potentially more dangerous, based on my experiences with similar flipping kicks in Capoeira, is partial hits. Actually hitting with one of these kicks will rob you of some of your momentum, and may change your direction of movement as you are deflected, which puts you at greater risk for landing badly, whether it's on the head or spine, or awkwardly catching yourself with your limbs. Even if you avoid damage on impact, you are likely now on the ground, which is a bad place to be if your opponent is still standing and able to capitalize on it, or they have buddies. Ideally, you should do some training against resistance to learn how to recover, and how to protect yourself in the case of a fall.
So where does this kick potentially come in handy? Well, generally it would be used in a one-on-one situation where you have only one opponent. It is a very powerful kick, and might be a decent way to break through a guard, or to strike a larger opponent, in a one-on-one situation. And in the case of a retreating opponent, it has the potential to attack while keeping in attacking distance. Even with a miss, you may be able to roll right back up to your feet and be within striking distance. Lastly, it might be a useful thing to train for those situations where you do lose your footing and want to try to salvage it into an attack. Ultimately, it's not a technique I'd have in my usual arsenal for a fight, but I see a definite benefit in learning it, both so that it could be used where appropriate and also, as with other flipping techniques, to teach air awareness for the situation where you have no choice but to be inverted during a fight.
Lastly, there is one other aspect to jumping, flying, and flipping kicks like this that's relevant to self defense, but less directly. Namely, because these attacks look impressive, they can sometimes be used to intimidate attackers to convince them not to fight you. Personally, I think the converse can also happen, where doing an impressive technique can lead to people wanting to fight you because of that, but there is a degree to which a drop-kick or even a non-offensive flip can lead to people going "Hey, that guy knows some moves... maybe I will take him up on buying me a beer to replace the one I spilled when he bumped into me."