My 2 cents.
The purpose of these videos is to feature the sounds of the Genos, not to sell the ability of the demonstrator to sing.
I want to her the sounds available on the Genos, not the sound of the demonstrators voice while playing chords.
Everyone can sing but not everyone can sing well. No amount of vocal training is going to transform a person without some degree of natural ability into a good singer. Everybody can sing but not everybody can carry a tune in a bucket. Singing is a talent that people are born with.
Locally, I hear comments about musicians that are fantastic players, but they should stop singing. They were good singers at one time, but have lost it over time, and people stop coming to hear them.
As far as the vocal harmony on the keyboards, most people don't set them up properly for the individual singing. My singer loves the VH on my Tyros, and it sounds very good used in moderation. She has a voice that works very well with the VH. I've had other singers that I couldn't use it with.
Regards,
Jerryghr