It is a wrong narrative.
The Soviet SSRs were a result of the decolonization process in the former Russian Empire.
Some of them were arguably that, though I would rather talk about ostensible political devolution of powers to subnational entities within the context of the USSR. Others, namely the Baltic SSRs, were the result of Soviet expansionism after the breakup of the Russian Empire (which in itself was an example of decolonization).