timing belt replacement

I have an 04 sonata, basic model 4cyl. I discovered a strange thing while reading the maintenance schedule. Timing belt is to be replaced at 60,000 miles. However there is a small notation next to it. Down at the bottom of the page it states, " except in the state of california". Whats up with that? Nobody but nobody , including the service manager at the dealership could give me an answer. What, different belts in cal, different air quality and less belt deterioration. Makes no sense to me.