There's a bit more to "High Concept" than what is in that article. To be sure you have a High Concept. It need to be "Uniquely Familiar" and also, it NEEDS to show the promise of Conflict.
Uniquely Familiar:
Unique: = the "hook" of an idea. It needs to offer something, new, fresh and compelling to the reader. It needs to capture interest.
Familiar: = it must be able to resonate with universal human emotions
A High Concept got to be able to be encapsulated in a sentence or 2 (less than 25 words), be easily understood by anyone. (An original twist on an already familiar, marketable idea)
Ruthless People was a good example of this. It took a familiar, marketable idea (a kidnapping of a man's wife) and put a twist on it (he's delighted that she was kidnapped)
It must have Conflict and HIGH STAKES (the hero has alot to lose if he fails)!
Karl Iglesias has a great dvd on Concept in screen-writing (it's where I got the majority of my information regarding concept from, including what I've just written)