If I remember correctly, and if you listen carefully to what Jurij says, you will find that the level of torsional stiffness is what make a ski suitable for beginners/experts.
Take a look at this for the Mantra M6 and Blaze 86. It is not a perfect comparison (there are a few factors that are changing like the width and the mass), but it gives you an idea. I plotted the short and long length so that you can see how the lengths of each model scale. The Blaze 86 is marketed as an intermediate ski. The Mantra is an advanced/expert ski.
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The bending stiffness differences between comparable lengths is about 15-20%. That is not very much. Bending stiffness is related to the speed limit of a ski, and if you think about it, the vast majority of people at resort ski at relatively comparable speed (beside a few chosen one).
The torsional stiffness differences between comparable lengths is however on the order of 60%. This makes a ski precise vs playful. A beginner doesn't want a precise ski. They don't have the skills to prevent catching an edge, or deal with the situation once it happens. Expert skier might want either precise/grippy or playful depending on the feel they are looking for.
Thanks, that's good.
Re-listened to the Jurij interview. Just to make sure we're listening to same it's the Tom Gellie one. Seems it's a combination of both. What he says is their measurements showed the torsional stiffness didn't have any influence on how the ski was holding as long as the skier was in the correct fore/aft position. But as soon as the skier was a little forward or back of the binding area then the torsional stiffness made a huge difference.
The relevant discussion is about the 18 minute point in the interview and the bit about measuring the torsional stiffness was around 20 minutes.
Of course Jurij's era at Elan was a while ago.