I don't think that is true. I think most people would agree the people in Crimea understand they speak Russian, have a Russian passport, can travel inside Russia, pay taxes to the Russian government, their children are schooled in Russian topics. Culturally the majority probably feel quite Russian, or as Russian as any other "republic" of the Russian "federation".
There are countries with less cultural and linguistic similarity, for instance Catalonia comes to mind, yet there is also the general agreement that Catalonia is part of Spain and not fully self governed, much less governed by any other country.
Well it is more of... Hungary takes tanks and goes to Romania because there is large hungarian population and aquires some of their land with 50% romanians and if they leave they take their property. They started giving hungarian passports left and right in the past... with some kind of hope of leverage on other countries. Not as mas or menos independent community that wants(at least some part) to leave as is happening in spain.
There are countries with less cultural and linguistic similarity, for instance Catalonia comes to mind, yet there is also the general agreement that Catalonia is part of Spain and not fully self governed, much less governed by any other country.