One can get very picky about the way these sorts of experiments are performed, but I'll try to stay away from that. However, trying to identify differences in sound due to the back woods when the T(1,1)1's and T(1,1)2's range over a semi-tone on non-live back instruments (no T(1,1)3's apparent, Fig 1A) doesn't give you much of a chance.
How the back and sides are treated can make a huge difference to the way a guitar sounds. Live vs. non-live backs, mass loaded sides etc. are ample proof of that. But what wood you use, much less so, UNLESS you systematically rely on the average species properties rather than build technique to effect the differences.
What you hear when a guitar is played are the modal resonances, defined by their center frequencies, amplitudes and bandwidth. If you can measure the mechanical properties of the wood (density, Young's modulus, damping) and use the right, well documented techniques, you can match the important modal resonances of guitars made of different woods pretty closely. That's what builders are doing (whether they realize it or not) when "The guitar maker, by treating each back in the way that his experience suggested was best, has to a very large extent compensated for any physical differences between the types of wood
". So a wide range of woods can be made to sound alike, which means, of course, that players can't pick the difference, and guitar builders have a much greater range of woods at their disposal. I know that I can't pick wood species on my (modally tuned) guitars. All we need to do now is stop the dealers from perpetuating the species myths and get them to promote some of the more sustainable alternatives.