Unbelievable

Maybe the forgot the “comma” after the word  “finish”

All I know is that lacquer is important to piano manufacturers, as its use is correlated to the hammer stiffness/density and consequently the sound character we call brilliance. The lacquer/varnish used by Stradivari is the main reason why his violins can not be replicated.
How does it translate to the loudspeakers I have no idea. I remember though that piano lacquer and glue were mentioned in relation to the discontinued Bosendorfer speakers which were rather special.
It may depend on design. If Yamaha use the "sounding board" principle employed by that Bosendorfer, then the glossy lacquer will definitely affect the sound. If the cabinet is damped, then it does not matter whatsoever.

PhD  the pic up are not bad , I leave the guitar the way it is , any mods on guitars in my opinion, degrades it . Not original ,anymore I have Gibson’s already, sorry for going off topic.

I have used varnish on black colored tweaks for the past decade. Different colors give a different sound signature. The neutral colors are white or black. White has an open and transparent sound while black has a blacker background, but also dark, muddy and veiled sound. By using varnish on top of black paint you compensate for the veiled sound and add clarity. This gives good balanced sound.

Interesting....