I think the GP is a bit confused and mixed Lithuania up with its neighbors. Lithuania, unlike its neighbors Estonia and Latvia, gave citizenship automatically to everyone residing in Lithuania right before the independence. While Estonia and Latvia chose to create a naturalization process aimed at excluding ethnic Russians.
All Russians born in Lithuania been offered Lithuanian citizenship, repeatedly, many times over.
Some Russians on the far right of the political spectrum repeatedly imply the contrary. This is not even a conspiracy theory, but a "being debunked in 5 minutes Googling theory."