only thing i dont quite agree with is the idea of a guitar as purely subtracting potential string energy. I think there is a certain amount of body/neck vibration fed back into the string which is also an important part of tone.
This is it though, isnt it? The string is capable of developing huge amounts of overtones, being a thin, linear piece of metal. The guitar, being a big clumsy bit of wood is capable of developing far fewer overtones. The string-guitar combination is a resonance feedback loop; initial excursions of the string excite resonances in the guitar, the guitars resonance feeds back to the string, and thats where the guitars tone happens; the string is forced to carry only the overtones allowed by the guitar; just the modes that its capable of resonating with, since in the guitar-string loop all overtones in the guitar and the string must be in phase
The way I see it, very simplified, is a circle. You can have standing waves on a circle. Half the circle is the guitar from nut to bridge and half is the string, its a complete vibrational loop, and whats on the string half is only whats allowed on the guitar half. You cant have a situation there where theres a 10th mode on one half thats not on the other, and the guitar is the bottleneck.
Obviously the situation is a lot more complex than that, but its still generally true to say that the modes allowed on the string are the modes allowed by the guitar. I'd have thought that was relatively uncontroversial and struggle to see how the guitar can possibly add any sort of vibration that didnt start in the string, since its purely a resonator.
I've never been terribly impressed by the PRSes I've played, but in the general indications of the philosophy that hes getting at, hes completely right, the guitar is just subtractive, and the closest thing to objectively 'better' you can get is a guitar that transmits vibration most efficiently across the widest frequency range (to give you the most to work with down the line).
As far as tone being in the fingers....yeah, very much so, but I'll give you a stock strat, fender twin, 2x10, SM57 and a million years to get a close reproduction of the guitar sound off the black album ;) Do you need hetfield, or someone that can play a lot like him, as well? Yes. But even with the right player, you need a lot more besides.
