A lot of Far Eastern cuisines are not made by the people you think. My parents ran a Thai/Viet mix place for a while, after having run a Chinese place. If you go to one of my favorite sushi shops in London you'll find people speaking Cantonese.

I think what happens is the restaurateurs see what's popular and figure they can pass for whatever other group it is. And the food is like software, you can learn another framework reasonably well if you have the fundamentals and a little experience.