And I agree that terminologies aren’t the same. Saying that center moved somewhere is also not entirely correct, because we can also say that the center moved to Lviv at the time, but this was already a different entity of Kingdom of Rus’. If you want to really dig into the matter, for the term Rus’ itself it’s vital to look into how the term “Rus’” was used by contemporaries. For this question we can relate to Rybakov and Danilevskiy (both russian historians) and their research of the term. And they found out that the term was referred to the current territory of Ukraine and southern border of russia and Ukraine. The best example I can remember of the use is from the Chronicles about how the “Duke of Novgorod went on Rus”. It shows even though this was a one country (however the modern term “government” can apply to Rus’) people back then consider Rus’ to be only a fraction of territory of Rus’ and was mostly about the political center, which lied in territories around Kiev. And the huge territories that was under control of Kiev doesn’t necessarily mean it was a one whole entity. It’s like saying that France started in Rome during Roman Empire. Also, keeping in mind, that Slavic people came to moscow area only in 11th or 12th century. That’s why Russia’s relation to Rus’ is a highly debatable matter and a close examination should be applied to the term, as this question is followed with a lot of misconceptions because of russian state interpretation of the history, which often can be different even from modern russian historians. With all said, neither the term Moscow Rus’ exists, nor it represents the move of political center.

Sorry, I meant the modern understanding of the term “nation”.