I don't recall Kevin blogging about startups. It was a movie. Honestly, this title seems a little over the top.
As for the advice... It's good but there is a world of difference between testing something you've built and asking people if they'd want something you haven't built. In "The Innovator's Dilemma," the case of excavators is used as a case study.
If you had asked construction managers whether they wanted hydraulic excavators instead of cable excavators, they would have laughed you out of the industry. The hydraulic excavators of the day were flakey and much smaller than the cable excavators. Nobody who was using excavators would want one.
The point was that hydraulic excavators ended up creating entirely new markets. Likewise, my own personal example is the GUI. I remember when this was just a research fancy at Xerox. I used a Xerox Star at Humber College in Toronto. Great stuff, but priced in the stratosphere.
If you'd asked anyone whether they needed a mouse and bitmapped screen to replace their CP/M word processor, you would have been laughed out onto the sidewalk.
Yet look at what we have today. Some things should be shown, and even then you might have to keep plugging until a light goes on and some entirely new market (like desktop publishing) springs up to use your innovation.