There are millions of people currently living who were born in the Soviet Union and about 0% of them identifies or is identified as “Nationality: USSR”.
I think what matters is whether the existence of an independent country is contested. No one contests non-existence of USSR but Tibetan case is not closed.
Maybe because the USSR was an artificial construct very few people identified with? Even when it existed, people were calling themselves Russians, Latvian and so on, not really "Soviet."
I think what matters is whether the existence of an independent country is contested. No one contests non-existence of USSR but Tibetan case is not closed.