I am betting it is either a warranty issue or competetive issue. In some countries routine service is covered for the first X years or miles, so having a longer interval means this work may not have to be covered by Kawi. Same could be said for warranty cover.
From a competition standpoint, if the SV or other bikes in the Versys price/value class have longer intervals, then Kawi would extend it to meet them.
And finally I wouldn't rule out dealer support, at least in the USA, lower intervals mean more service work for dealers.
I am betting my left nut that there is NO DIFFERENCE in material and other settings, it is just a marketing thing. the cold weather does not change the structure of the metal or its tolerances, only wear will do this, so again, I am betting it is a marketing thing.
Finally, CA is Canada, we here in the USA must remember that the United States is not the center of the universe and the world around us does not speak nor care about our state codes. There should be no specification change for California models when it comes to valve checks.