Some years ago I read a number of articles that different varnishes can affect sound, so maybe not too far fetched
Unbelievable
Yamaha really made this statement:
Glossy black piano finish provides improved signal-to-noise performance
https://europe.yamaha.com/en/products/audio_visual/speaker_systems/ns-5000/index.html
I thought I would seek opportunity to hear these speakers, but now I do not think so