How about if they have a machine which flexes the highback with a constant pressure until it snaps? You can then compare highback stiffness.
and yeah, there is 3% more torsional flex this year.
If the material composition of the highback was altered slightly, and tests were done as described above, then the 3% sounds like it could just be a number the marketing team got ahold of.
Unless, combined with other changes in re:flex or whatnot, the sum of the small changes would be somehow noticeable.
I bet the margin of error for the stiffness of run of mass produced highback pieces is at least 1.5%.