It is not like that at all. For genealogy prior to 1971 you are not required to submit any type of identity card such as birth proof of parents or ancestors. This was valid only for the Assam NRC based on the simple agreement and the directive of the Hon'ble Supreme Court. For the rest of the country, the NRC process under The Citizenship (registration of citizens and issue of national identity card) Rules, 2003 is completely different.