Indeed. And in history, the alliance didn’t even last that long lol. There was a falling out over the Korean War (USSR promised aid but ended up making China do most of the lifting) and tension along the border of the USSR and China was quite high. They had fallings out over many slights and differences. The idea of a monolithic USSR-China Communist bloc was fantasy but potent enough to make the US to try to prop up Vietnam (“domino theory”). Both the USSR and China were too big and powerful and close to fully trust each other. President Nixon helped cement China’s diplomatic move away from the Soviet Union with his visit.
https://en.m.wikipedia.org/wiki/Sino-Soviet_split
Another thing you might not know: China invaded Vietnam not long after the US left, over differences over influence in Cambodia. Not a lot of love lost there between those two Communist countries, either.
https://en.m.wikipedia.org/wiki/Sino-Vietnamese_War
This has been your random history lesson of the day.