A lot of the styles are made by the demonstrators of the manufactures and those that do work for the manufactures; in addition many of the concert artists also do style development work for the manufactures. (Thus plenty of interviews about)
Most western style development is done in the UK and Germany as they have the largest markets for arranger keyboards. (Again you will find many interviews in the various magazines available)
Bill
can you please send me the links to those videos and interviews ? my search and browse skill must be terrible because Ive been watching videos about keyboards and sometimes reading music magazines for over 20 years and haven't found a single interview of such sort