Why aren’t NE diaspora considered as people of Indian origin?

Foreigners whose ancestors were indentured Indian labourers in Fiji, Suriname, Trinidad, Malaysia etc are considered to be Indian diaspora and the Indian govt has many outreach programs. The OCI card eligibility has already been extended to Surinamese Indians. However, Manipuris or Assamese who were captured and taken away by Burmese invaders in early 19th century and whose descendants now live in Burma aren’t considered people of Indian diaspora. I doubt anyone even knows about them other than their own people. Even for Naga or Mizo people who are ostensibly Indian people and saying otherwise is considered treason, the same people Naga or Mizo people across the Burmese border are not considered Indian diaspora. For Bangladesh and Pakistan, it’s understandable because there was a religious partition wherein the people fought and killed each other. But it’s unbelievable that Nagas, Mizos or Manipuris and their entire people and culture are claimed as Indian but their diaspora is not. It’s a double standard because if they were Tamils, Biharis, Gujjus - it won’t be so.