All that question mark kick is is a roundhouse to the head.
Well, I don't know that much about titles of moves in TKD, but I think we used to consider a roundhouse a kick from the back foot. That was also almost always the leg that had about 70% of our weight. You could see it coming but if it connected with anything, if carried a lot of power.
But this is a little different than what people are talking about, just like the one above at post #14, and about the 14 minute mark in post #10. The setup is to kick low towards the ankle of low shin. You don't even have to connect. It would normally be expected that the kicker, when he pulls the leg back after the miss, is going to step all the way back to miss a quick counter attack. Instead, the kick comes to the head/face with pretty good power. Even if there is no knockout, it will rattle the opponent. Of course, you do need good balance at all times. I'm not sure that is always stressed these days. We were always taught to be perfectly balanced at all times, knowing that might shorten some kicks or punches. But it gave more power.
Jhoon Goo Rhee, in the mid-sixties, taught that kick. He had two signature kicks, one of which he demonstrated publicly. He would do a side kick to the face. It had so much power that his gi would strike his leg with enough force to make a loud crack. He would move his foot back a bit and kick again, with the same slap, and do that one more time before he returned to having both feet on the floor. Trust me, it was impressive and something the rest of us practiced. I don't recall anyone getting a slap on the first kick, much less a second or third kick, if we could keep our balance for a second or third, it still wouldn't have much power except for the first kick. So yes, it can be done. But not by many.