There's many testimonials on the Web about vintage wiring brighter sounding than modern one even with pots full up and... that's my subjective experience as well (shamelessly).
Some people would probably attribute that to psychoacoustic.
Personally, I've encountered way too many unexpected phenomenons with guitar electronics to discard the possibility of some unseen interaction. After all, a guitar signal is amplified several hundreds of times by a typical amp so it's not shocking to think to minuscule differences as becoming finally perceptible. Frank Falbo did evoke such things in his posts years ago.
To be honest, I've not dug the question theoretically. But if I do it and if time permits, I'll share my findings.
Back on topic, to put in perspective my previous answer: vintage LP wiring was good with low-fi vintage rigs including non buffered signal paths, warm sounding loudspeakers and so on. I've rarely played a vintage circuit without finding it softer than modern equivalents and I think it's not only due to aging but also to modern components being more consistent and efficient.
The tricks evoked in my previous post are a way among others to make the sound like when guitarists were plugging their guitars to their amps through 9m of coily cable or things like that. It makes a BIG difference.
For the record, the strap mounted Fryer treble booster designed for Brian May hosts a cap meant to emulate the missing cable from guitar to amp and this cap measures 4,7nF: it's enormous. like 30m of wire or more.
Santana has a "sweet switch" in his PRS guitars, doing the same thing thx to a delay line (equivalent to a series of inductors separated by capacitors to ground: more refined than a crude cap but not that different either)...
And the smoothing effect of stray capacitance is
everywhere. Yesterday, I was "tuning" a pedalboard including a treble booster followed by tube driven OD/dist pedals: with this path directly followed by a buffered pedal, the tone was awfully harsh. Through a true bypass pedal, it was perfect.
Enough said: the sound of passive magnetic pickups is too often considered independantly of the whole signal path IMHO. Each transducer has an optimal electrical environment, different for a P.A.F. replica than for a high gain PU.
FWIW (tedious rambling of an old fart while the house is still sleeping a Sunday morning).
