Michelin has always been accused of being biased towards French food but this list makes it seem they like sushi more.
I don't know about biased in case of Japan. Japan leads the world in luxury goods sales thus it would make sense Japanese being interested in high quality food.
I don't think it's just sushi, it seems like the majority of East Asian cities have many Michelin-starred restaurants.
Michelin guides have biases. For example they are big into basque cooking. If you want, you can go to northern Spain and in an hour you can book about 15 Michelin stars worth of meals over a week. And the population of those towns are only like a few hundred thousand. It's not like tokyo is a cosmopolitan city like NYC or London where chefs from all over are experimenting with new cuisines.