regardless of whether or not the finish on the front of speakers can affect the reflected sound, the advertisers have probably never met the engineers, so I say go ahead and listen...
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