my TKD teacher was Billy Hong, who was All-Asian TKD champion in 1966 & 67. The first day he showed up at our dojo, he walked in (in his street clothes), kicked off his shoes, and then walked over to the wall. He was standing about a foot from the wall, and brought his leg out and up over his head and put his foot flat against the wall. That got our attention...
He too had that vertical kick, and could make it happen in very little space... but his blocking skills sucked. I had been doing Okinawan karate and Shotokan, and had a combination that began as a front snap kick, and then changed to a roundhouse to the head. Billy never could block it, and would always shout at me "you use illegal kick" (x 3). What made it "illegal" was the fact he couldn't block it.
I wouldn't short-sell TKD at all, because one of the championships Billy won was when he broke the jaw of the competitor through one of those old "wire masks" that we used for full contact fighting. He was like trying to fight a weedeater... and there were feet flying at your face wherever you were... so, as you say, it's the "singer", not the song. He was very, very good... but he wasn't invincible. I used to pi$$ him off greatly by using that snap-roundhouse combination simply because I knew he couldn't block it. I didn't have nearly the skill at that time that he had, but I had his number with that one technique... and could get him stomping mad by using it.
He was a good teacher, and TKD in this area is mostly because of his efforts and from his student base. He was killed on flight 007 that was shot down by the North Koreans when he was returning home from Seoul. I enjoyed training with him, but we never really got along together.
I was a Shodan and he was 4th degree at the time, and while we didn't really make friends, we both respected what each other could do. Walking out of the dojo one night, one of his students (brown belt) asked "what makes him a black belt?"... "he doesn't know our katas," etc. and he threw a kick at my head from beside me. I blocked it about 2" from my head, and Billy stepped between us and said... "that's the difference"... and proceeded to take one of his brown belt ranks away from him.
I asked him later why he did that, and he said "I don't need stupid
blackbelts coming out of my school. He was a real piece of work, and had been doing TKD for 14 years when I met him... he was 22 or 23 years old, and had been an orphan in Seoul, and all he did was go to school and then do TKD.
He was one of those "wicked fast" guys you're talking about...