This is total nonsense. The Baltic republics completely ignored the Soviet constitution, their declaration of independence was entirely unilateral and decided on not by referendum but solely by a parliament elected in farcical bourgeois manipulated elections that followed the disastrous perestroika reforms. And the text of the declaration was full of historical revisionist lies and promises they never intended to keep, like in the case of Estonia for example they said they were declaring independence so they could pursue their own path to socialism, and that they would never pass laws discriminating against other ethnic groups. Yet immediately after they went on to dismantle socialism and pass laws that took away the citizenship of ethnic Russians and excluded them from being able to buy land or hold certain jobs.