I think that's very true. The East European Jews lived in their own communities and had a distinctive Yiddish-speaking culture, qualifying them as a nation, albeit an oppressed one which didn't enjoy sovereignty over its own territory.
[WS:] I do not think that Western concepts of nation-state sovereignty fits well the 19th century Eastern European reality. None of the people in the 19th century Eastern Europe enjoyed sovereignty of the territory they occupied- at least in today's Western sense of the word. Eastern Europe is was, and still is, an amazing diversity of more-or-less ethnic groups living under the imperial rule of the Romanov or Habsburg empires, and on the top of it, under the feudal rule of the landed gentry. Serfdom (not much different from North American slavery) was abolished in Russia only in 1861 but the de facto domination of the landed gentry persisted until 1917. Unlike EE peasantry, Jewish communities were at least exempt from the latter, and enjoyed considerable level of local autonomy.
Wojtek