No, the videos point was that no matter what FLEX you use. They were trying to isolate the importance of FLEX. As they said in the video the primary influence the shaft has is on how if feels to the golfer. You wont be seeing drastic changes in actual numbers.
Now how it feels is based on the Bend Profile, the weighting, the clubhead weight, and how the club loads in the golf swing. Which if you want to say extra stiff is how much it can bend, then yes flex is a very OVERLY SIMPLISTIC way of saying that. Yes you probably wouldn't fit a high swing speed to a very soft bend profile (less stiff shaft). There is probably a correlation between swing speed and certain overall stiffness in bend profiles. Yet there is no significant difference in the actual launch monitor data.
Right, I meant flex specifically, but I got careless in writing there at the end.