I believe their mindset is providing keyboards for the elderly retirees, who at least have the advantage of such poor memory retention that the scat voices might NEVER get tiresome!
Perhaps one of the Yamaha software third party guys can invent a program that automatically replaces all the overdone vocals on the styles with less gimmicky sounds... Otherwise I envision lots of late night sessions editing all your styles by hand!
Thank God they didn't come out with an SA2 Kazoo!