He offered no reason for the correlation or why the chemicals discovered changed sound emanating from the instrument
He did actually. His claim is that the various nanoparticles in the varnish and embeded in the wood dampen high frequency noise which brightens the sound. Since these kinds of materials properties are not normally the subject of the kind of analysis that physicists analyze for in modeling the acoustic modes of the string and sound box, they would not have been discussed before.
What is unique in his analysis is the coupling of new results from chemical analysis to the accoustic properties of the instrument.