You're starting with the concept of "Russian SSR" to mean "Russia" and going from there, and this line of reasoning makes sense. But really, "Russian SSR" was t

You're starting with the concept of "Russian SSR" to mean "Russia" and going from there, and this line of reasoning makes sense. But really, "Russian SSR" was the novel concept. Before the USSR, "Russia" meant the "Russian Empire", which comprised of basically the same area as the USSR. So during the time of the USSR, "Russian SSR" had no meaning (to the West), it's only significant now in hindsight after the breakup. To summarize this perspective I'd view it like this: The "Russian Empire" i.e. "Russia", was renamed "USSR" and internally they drew lines to make states, for which "Russia Core" for lack of a better name was simply called "Russian SSR".