Yamaha have done exactly what was asked for.
I tend do disagree, Eileen. With the Kbd parameter you could select the parts that should be affected. Of course, we expected this for the KbdVol paramater too, which is an obvious requirement.
I think a much better solution would be to have a dedicated bus in the mixer for the keyboard parts. We have such buses already for Style (applies to 8 Style parts), Song (applies to 16 Song parts) and Muti Pad (applies to 4 Multi Pad parts). By default the Volume for these buses is 100, so you may not only decrease the volume but also to increase the volume of a Style/Song/Multi Pad as an entity, if needed. Very convenient.
The keyboard bus should be configurable, so you could choose which of the keyboard parts are routed to this bus. IMHO this would be a very flexible solution. It would solve the flaws of that new KbdVol parameter, offer new possiblilites and it would be easy to understand, because it's consistent with the buses we already have in the mixer.
This would be a major change in the Mixing Console, but hey, Yamaha's vision is clearly to be a world class company, so they should be able to do it
.