I don't know honestly, but I think they should include the Niseis and Sanseis as part of the Japanese citizens, IF they aren't detached from the culture. Like with me, I find it illogical to even grant me a chance at getting a dual citizenship with India, since I am so far removed from being Indian, in terms of mannerisms and behavior. Also, I can't speak the mother tongue.
The thing I'm trying to point out is like, if those second and third generations somehow were able to maintain their cultural-ethnic background and practices, they should be somewhat considered, no? In every sense, the essence of being Japanese is still being passed onto the next generation without having been born in the mainland. Of course, I'm not saying all second and third generation offsprings are like this, I've lived in America long enough to know that most "Asian-Americans" are just pretty much Americans now who have no idea about their own cultural origins, so their claims of heritage for it is flimsy at best (which is why I don't really like the casting of Asian-American actors in Asian roles, they are pretty much clueless to their own backgrounds). At least I know enough of my own ethnic and cultural background's history that my parents tried to teach me about, but I don't even think it's enough to even say I belong to it because my mannerisms and behavior is more in line with a Westerner, somehow with predominantly Eastern values at it's core. I just know that, it's a thing that there are those like that out there, the ones that have proper claim. I mean, despite what I've said about myself, there are also Thai-Indians here who can slip back into the India and be a citizen quite easily, I'm just kind of a black sheep.