Oh, I believe you. I'm wondering if they didn't sell them in California for emissions reasons or something. I was a HUGE Yamaha fan at the time and actually collected the brochures every year until they stopped producing individual model pages.
My first bike was a JT-1 (the GT80 predecessor), Dad had a '75 DT125 and I lusted hard for the 1979 DT100 before skipping to a YZ125 and my sister ended up getting a 1980 DT100. I knew the series very well, just don't remember ever seeing it in street legal form.