It fit USSR interests to say that they were the standard bearer of communism back in the day. It fit US interests to say exactly the same. Neither had any reason to think about how the word was used prior to the USSR and if it actually applies at all.
It's no wonder that people who lived behind the Iron Curtain have just as bad an understanding of communism as people in the US. The USSR certainly didn't want you reading theory outside of Marxist-Leninist material.